Journal of Physics B: Atomic, Molecular and Optical Physics - IOPscience

Journal of Physics B: Atomic, Molecular and Optical Physics - IOPscience
Journal of Physics B: Atomic, Molecular and Optical Physics
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Journal of Physics B: Atomic, Molecular and Optical Physics
covers the study of atoms, ions, molecules and clusters, and their structure and interactions with particles, photons or fields.
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Rydberg atom quantum technologies
C S Adams
et al
2020
J. Phys. B: At. Mol. Opt. Phys.
53
012002
View article
, Rydberg atom quantum technologies
PDF
, Rydberg atom quantum technologies
This topical review addresses how Rydberg atoms can serve as building blocks for emerging quantum technologies. Whereas the fabrication of large numbers of artificial quantum systems with the uniformity required for the most attractive applications is difficult if not impossible, atoms provide stable quantum systems which, for the same species and isotope, are all identical. Whilst atomic ground states provide scalable quantum objects, their applications are limited by the range over which their properties can be varied. In contrast, Rydberg atoms offer strong and controllable atomic interactions that can be tuned by selecting states with different principal quantum number or orbital angular momentum. In addition Rydberg atoms are comparatively long-lived, and the large number of available energy levels and their separations allow coupling to electromagnetic fields spanning over 6 orders of magnitude in frequency. These features make Rydberg atoms highly desirable for developing new quantum technologies. After giving a brief introduction to how the properties of Rydberg atoms can be tuned, we give several examples of current areas where the unique advantages of Rydberg atom systems are being exploited to enable new applications in quantum computing, electromagnetic field sensing, and quantum optics.
The following article is
Open access
Atom based RF electric field sensing
Haoquan Fan
et al
2015
J. Phys. B: At. Mol. Opt. Phys.
48
202001
View article
, Atom based RF electric field sensing
PDF
, Atom based RF electric field sensing
Atom-based measurements of length, time, gravity, inertial forces and electromagnetic fields are receiving increasing attention. Atoms possess properties that suggest clear advantages as self calibrating platforms for measurements of these quantities. In this review, we describe work on a new method for measuring radio frequency (RF) electric fields based on quantum interference using either Cs or Rb atoms contained in a dielectric vapor cell. Using a bright resonance prepared within an electromagnetically induced transparency window it is possible to achieve high sensitivities, <1
V cm
−1
Hz
−1/2
, and detect small RF electric fields
V cm
−1
with a modest setup. Some of the limitations of the sensitivity are addressed in the review. The method can be used to image RF electric fields and can be adapted to measure the vector electric field amplitude. Extensions of Rydberg atom-based electrometry for frequencies up to the terahertz regime are described.
The following article is
Open access
The Landau–Zener formula made simple
Eric P Glasbrenner and Wolfgang P Schleich 2023
J. Phys. B: At. Mol. Opt. Phys.
56
104001
View article
, The Landau–Zener formula made simple
PDF
, The Landau–Zener formula made simple
We employ the Markov approximation and the well-known Fresnel-integral to derive in ‘one-line’ the familiar expression for the Landau–Zener transition probability. Moreover, we provide numerical as well as analytical justifications for our approach, and identify three characteristic motions of the probability amplitude in the complex plane.
Multiple-harmonic conversion of 1064 nm radiation in rare gases
M Ferray
et al
1988
J. Phys. B: At. Mol. Opt. Phys.
21
L31
View article
, Multiple-harmonic conversion of 1064 nm radiation in rare gases
PDF
, Multiple-harmonic conversion of 1064 nm radiation in rare gases
The authors report the observation of very-high-order odd harmonics of Nd:YAG laser radiation in rare gases at an intensity of about 10
13
W cm
-2
. Harmonic light as high as the 33rd harmonic in the XUV range (32.2 nm) is generated in argon. The key point is that the harmonic intensity falls slowly beyond the fifth harmonic as the order increases. Finally, a UV continuum, beginning at 350 nm and extending down towards the short wavelength region is apparent in xenon.
The following article is
Open access
Roadmap of ultrafast x-ray atomic and molecular physics
Linda Young
et al
2018
J. Phys. B: At. Mol. Opt. Phys.
51
032003
View article
, Roadmap of ultrafast x-ray atomic and molecular physics
PDF
, Roadmap of ultrafast x-ray atomic and molecular physics
X-ray free-electron lasers (XFELs) and table-top sources of x-rays based upon high harmonic generation (HHG) have revolutionized the field of ultrafast x-ray atomic and molecular physics, largely due to an explosive growth in capabilities in the past decade. XFELs now provide unprecedented intensity (10
20
W cm
−2
) of x-rays at wavelengths down to ∼1 Ångstrom, and HHG provides unprecedented time resolution (∼50 attoseconds) and a correspondingly large coherent bandwidth at longer wavelengths. For context, timescales can be referenced to the Bohr orbital period in hydrogen atom of 150 attoseconds and the hydrogen-molecule vibrational period of 8 femtoseconds; wavelength scales can be referenced to the chemically significant carbon K-edge at a photon energy of ∼280 eV (44 Ångstroms) and the bond length in methane of ∼1 Ångstrom. With these modern x-ray sources one now has the ability to focus on individual atoms, even when embedded in a complex molecule, and view electronic and nuclear motion on their intrinsic scales (attoseconds and Ångstroms). These sources have enabled coherent diffractive imaging, where one can image non-crystalline objects in three dimensions on ultrafast timescales, potentially with atomic resolution. The unprecedented intensity available with XFELs has opened new fields of multiphoton and nonlinear x-ray physics where behavior of matter under extreme conditions can be explored. The unprecedented time resolution and pulse synchronization provided by HHG sources has kindled fundamental investigations of time delays in photoionization, charge migration in molecules, and dynamics near conical intersections that are foundational to AMO physics and chemistry. This roadmap coincides with the year when three new XFEL facilities, operating at Ångstrom wavelengths, opened for users (European XFEL, Swiss-FEL and PAL-FEL in Korea) almost doubling the present worldwide number of XFELs, and documents the remarkable progress in HHG capabilities since its discovery roughly 30 years ago, showcasing experiments in AMO physics and other applications. Here we capture the perspectives of 17 leading groups and organize the contributions into four categories: ultrafast molecular dynamics, multidimensional x-ray spectroscopies; high-intensity x-ray phenomena; attosecond x-ray science.
The following article is
Open access
A simple method to extract nonlinear signals in time-resolved spectroscopy
Julian Lüttig and Pavel Malý 2026
J. Phys. B: At. Mol. Opt. Phys.
59
063001
View article
, A simple method to extract nonlinear signals in time-resolved spectroscopy
PDF
, A simple method to extract nonlinear signals in time-resolved spectroscopy
Time-resolved spectroscopy such as pump–probe and related techniques is the method of choice to observe molecular processes at the femtosecond timescale. The interpretation in terms of excited particles relies on the perturbative expansion of light–matter interaction. The control of contributing nonlinear orders is, however, difficult: at low excitation intensities the contribution of undesired higher orders of nonlinearity is small but so is the overall signal-to-noise ratio (SNR). At high pump intensities the SNR is improved but higher orders of nonlinearity contribute strongly to the overall signal. In this tutorial, we discuss the recently introduced technique of intensity cycling that solves this long-standing problem. Intensity cycling is a simple procedure in pump–probe type spectroscopy that relies on systematic variation of the pump intensity allowing one to separate the nonlinear orders. The nonlinear signals of different order are constructed from linear combinations of measurements at specific pump intensities. We discuss the new fundamental processes that are now accessible through separated higher-order signals such as multi-particle dynamics and interaction. The method is useful especially in extended excitonic systems such as polymers, where it can extract clean single-excitation dynamics and probe exciton diffusion via exciton–exciton annihilation. We review the fundamental and technical challenges of intensity cycling and introduce the language of double-sided Feynman diagrams providing a systematic theoretical framework to describe the various nonlinear signal contributions. We also discuss the recent developments regarding extension and generalization of intensity cycling to other techniques such as two-dimensional spectroscopy. Since intensity cycling can separate nonlinear orders independent of the sample, the method is applicable to a wide range of scientific questions and provides an exciting new perspective of time-resolved spectroscopy.
The following article is
Open access
Autler–Townes splitting in Rydberg atoms: transition dipole matrix element extraction and field efficiency analysis
Brian C Holloway
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
035002
View article
, Autler–Townes splitting in Rydberg atoms: transition dipole matrix element extraction and field efficiency analysis
PDF
, Autler–Townes splitting in Rydberg atoms: transition dipole matrix element extraction and field efficiency analysis
We report the observation and quantitative analysis of Autler–Townes splitting in rubidium atoms excited to Rydberg states using a four-level ladder-type electromagnetically induced transparency (EIT) scheme and resonant radio-frequency (RF) fields. By fitting the EIT spectra to Voigt profiles and calibrating the frequency axis with a semi-empirical Rydberg–Ritz model, we extracted transition dipole matrix elements (TDMEs) for the
transitions across five principal quantum numbers:
53, 55, 68, 75, and 85. Comparison with theoretical predictions revealed systematic deviations in the Rabi frequencies, attributed to RF delivery inefficiencies and standing-wave enhancement within the vapor cell. To address these effects, we developed two complementary approaches: an empirical quartic fit to measured efficiencies and a physics-based model, capturing both transverse radial variation and dominant longitudinal interference along the cell axis. These models explain the observed scaling behavior, predict an efficiency peak near
≈ 60, and reduce TDME discrepancies to less than 5% at the validation point. Our analysis highlights the influence of spatial field distribution and cell geometry on precision atom–field interaction measurements and establishes a robust experimental framework for TDME extraction in ladder-type EIT systems.
The following article is
Open access
Simple Python tools for modelling few-level atom-light interactions
Lucy Downes 2023
J. Phys. B: At. Mol. Opt. Phys.
56
223001
View article
, Simple Python tools for modelling few-level atom-light interactions
PDF
, Simple Python tools for modelling few-level atom-light interactions
Understanding the interactions between atoms and light is at the heart of atomic physics. Being able to ‘experiment’ with various system parameters, produce plots of the results and interpret these is very useful, especially for those new to the field. This tutorial aims to provide an introduction to the equations governing near-resonant atom-light interactions and present examples of setting up and solving these equations in Python. Emphasis is placed on clarity and understanding by showing code snippets alongside relevant equations, and as such it is suitable for those without an excellent working knowledge of Python or the underlying physics. Hopefully the methods presented here can form the foundations on which more complex models and simulations can be built. All functions presented here and example codes can be found on GitHub.
The following article is
Open access
Angle-resolved photoionization of molecules
Philipp V Demekhin 2026
J. Phys. B: At. Mol. Opt. Phys.
59
053001
View article
, Angle-resolved photoionization of molecules
PDF
, Angle-resolved photoionization of molecules
This tutorial summarizes the essential theoretical background, underlying the angle-resolved photoelectron spectroscopy of molecules. It reports an analytic derivation of the differential cross section for the one-photon ionization of molecules, as well as further analysis and exemplification of the photoelectron angular distributions in the molecular and laboratory frames of reference. Aiming primarily at nonspecialists, it addresses theoreticians and experimentalists in this rapidly-advancing field of research and provides a brief list of theoretical methodologies for numerical calculations in molecules.
The following article is
Open access
Measurements of absolute cross sections from excited states via double resonance ion-imaging mass spectrometry: the
autoionizing Rydberg states of argon
Haw-Wei Lin
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
075001
View article
, Measurements of absolute cross sections from excited states via double resonance ion-imaging mass spectrometry: the autoionizing Rydberg states of argon
PDF
, Measurements of absolute cross sections from excited states via double resonance ion-imaging mass spectrometry: the autoionizing Rydberg states of argon
We demonstrate measurements of absolute cross sections from excited states via a double resonance scheme in an ion-imaging mass spectrometer. The method is applied to determine photoexcitation (PE) cross sections of the transition from metastable argon (Ar*) in the
state to the
or
Autoionizing Rydberg States (ARS) of Ar, whose lineshapes and cross sections are sensitive probes for high-level electronic structure theory. The Ar* atoms are generated via electron impact excitation in a pulsed supersonic molecular beam, and a subsequent
in situ
one-photon transition excites the Ar* atoms to the
and
ARS resonances that rapidly evolve into Ar
ions. The lineshapes of the PE spectra of the two ARS of Ar are in excellent agreement with published experimental spectra and high-level
ab initio
calculations. However, the measured absolute cross sections are systematically larger than the theoretical predictions by factors of 2–3, providing new benchmarks to constrain many-electron correlations, core polarization potential, and s-d mixing interactions in electronic structure theory.
Elastic and inelastic cross sections for electron scattering from BeF
Savinder Kaur
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
085202
View article
, Elastic and inelastic cross sections for electron scattering from BeF
PDF
, Elastic and inelastic cross sections for electron scattering from BeF
We report the first comprehensive investigation of low energy scattering from the open-shell polar radical beryllium monofluoride (BeF). The elastic and electronically inelastic cross sections are computed from the
ab initio
-matrix method. These cross sections are computed within the static-exchange, static-exchange-polarization and many-states close-coupling models. This enables a systematic assessment of correlation-polarization, basis sets and effects due to the
-matrix box radius. The ionic character of BeF plays a key role in shaping the ground-state
potential energy curve. The elastic cross sections show a strong scattering model dependence below 5 eV but converge at higher energies, with different basis sets yielding nearly identical behavior. A prominent
shape resonance is found near 1.50 eV in the static-exchange model and shifts to lower value with a reduced width in the correlated scattering models. There was no evidence of dipole assisted resonance unlike MgF molecule. Excitation cross sections are reported for the lowest two dipole-allowed transitions namely
and
. The Born-closure approximation is applied to correct the cross sections computed from few partial waves. The
-matrices were subsequently used to obtain the differential and momentum cross sections in SEP model. The total ionization cross sections are estimated from the binary-encounter-Bethe model. The peak value of 2.71 Å
occurs at 78 eV. The results constitute the first complete theoretical collision data set for BeF and provide critical input parameters for modeling beryllium-containing laboratory and astrophysical plasma.
Experimental investigation of coherence contributions to a non-equilibrium thermodynamic process in a driven quantum system
Krishna Shende
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
085501
View article
, Experimental investigation of coherence contributions to a non-equilibrium thermodynamic process in a driven quantum system
PDF
, Experimental investigation of coherence contributions to a non-equilibrium thermodynamic process in a driven quantum system
The entropy produced when a quantum system at thermal equilibrium is driven to a non-equilibrium state can be considered as having components from coherence generation and from a population mismatch. The entropy component which is related to coherence represents a truly quantum effect and can be calculated using two different decompositions, based on either the relative entropy of coherence or on the thermal state corresponding to the Hamiltonian dephased in the eigen basis of the actual state. However, the decomposition based on the relative entropy was unable to quantify highly coherent processes or processes occurring in the low temperature regime. We experimentally explored a general driving scheme (a non-equilibrium process) on a nuclear magnetic resonance quantum processor, and were able to isolate the contribution of coherence to irreversible entropy generation. Furthermore, we numerically explored an infinitesimal driving process to distinguish between high and low temperature limits. The thermal equilibrium temperature and the final energy gap were varied to establish the relationship among temperature, energy level spacing, entropy production and coherence generation. Our results indicate that the contribution to entropy from coherence is higher in the low temperature regime. We also verified a generalized Clausius inequality, which affirms that the irreversible entropy production is lower-bounded.
Spontaneous emission of a uniformly accelerated atom in a cylindrical cavity: resonant enhancement and suppression
Qiulong Cheng and Zhiying Zhu 2026
J. Phys. B: At. Mol. Opt. Phys.
59
085001
View article
, Spontaneous emission of a uniformly accelerated atom in a cylindrical cavity: resonant enhancement and suppression
PDF
, Spontaneous emission of a uniformly accelerated atom in a cylindrical cavity: resonant enhancement and suppression
We investigate a two-level atom interacting with a massless real scalar field inside an infinitely long cylindrical cavity, and calculate separately the contributions of vacuum fluctuations and radiation reaction to the mean atomic energy-change rate when the atom moves along the cavity axis. Using the formalism suggested by Dalibard, Dupont-Roc, and Cohen-Tannoudji, we analyze both inertial and uniformly accelerated motion, and discuss the behavior in the low-acceleration and high-acceleration regimes. For the inertial atom, we further introduce a finite cavity quality factor
to phenomenologically account for cavity dissipation, which regularizes the resonant singularity of the ideal lossless cavity and yields finite resonant peaks. For a uniformly accelerated excited-state atom in the low-acceleration regime, the energy-change rate remains finite at the nominal resonance points, but exhibits pronounced oscillatory enhancement near resonance. In certain parameter regions, the cavity result can exceed both the corresponding inertial result in the same cavity and the uniformly accelerated result in free space, revealing the combined effect of acceleration-induced broadening and the discrete transverse mode structure of the cylindrical boundary. In the high-acceleration regime, a ground-state atom may undergo spontaneous excitation, while the cavity resonance structure is strongly suppressed and the energy-change rate gradually approaches the corresponding free-space value. These results show that the cylindrical geometry can significantly reshape the radiative response of accelerated atoms, enhancing acceleration-induced effects at low acceleration while washing out cavity-induced resonances at high acceleration.
EDITORIAL: Celebrating the life and science of Joseph H Eberly
Peter L Knight
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
080201
View article
, EDITORIAL: Celebrating the life and science of Joseph H Eberly
PDF
, EDITORIAL: Celebrating the life and science of Joseph H Eberly
Measurement of Nb L
αβ
characteristic x-ray production cross-sections by 5.5–9 keV positron impact and advancements in the numerical-neural network method for solving the thick-target inverse problem
Kun He
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
075203
View article
, Measurement of Nb Lαβ characteristic x-ray production cross-sections by 5.5–9 keV positron impact and advancements in the numerical-neural network method for solving the thick-target inverse problem
PDF
, Measurement of Nb Lαβ characteristic x-ray production cross-sections by 5.5–9 keV positron impact and advancements in the numerical-neural network method for solving the thick-target inverse problem
Cross-section data for inner-shell ionization by low-energy positron or electron impact are crucial for understanding interaction mechanisms between incident projectiles and atoms near the threshold energy. However, such experimental data are scarce, and results from different experimental methods also show significant discrepancies, which highlights the critical need for the development of advanced measurement techniques. In this study, the yields of Nb L
αβ
characteristic x-ray were measured from a thick Nb target bombarded by 5.5–9 keV positrons. Additionally, we improved the Numerical-Neural Network method proposed by Wu
et al
from our group. Using this improved method, we inverted the thick-target yield data to obtain the Nb L
αβ
characteristic x-ray production cross-sections induced by 5.5–9 keV positrons. In parallel, we processed the experimental Al K-shell characteristic x-ray yields from a thick Al target bombarded by 5–27 keV electrons, which were published by Li
et al
from Sichuan University. From these data, we derived the Al K-shell ionization cross-sections. The derived cross-sections for both elements were subsequently compared with results from the MC-Neural Network method and theoretical distorted-wave born approximation (DWBA) predictions. The results show that the experimental cross-sections from the two neural network methods are in good agreement, with deviations within 5%. For Nb L
αβ
characteristic x-ray production cross-sections (5.5–9 keV positron impact), the DWBA theoretical predictions are 20%–30% lower than the experimental values from our improved Numerical-Neural Network method, and this experimental cross-section data was obtained for the first time. The Al K-shell ionization cross-sections (5–27 keV electron impact), derived using our improved numerical-neural network method, agree well with published ratio-method results, while corresponding DWBA predictions are 7%–14% lower than our values.
The following article is
Open access
A simple method to extract nonlinear signals in time-resolved spectroscopy
Julian Lüttig and Pavel Malý 2026
J. Phys. B: At. Mol. Opt. Phys.
59
063001
View article
, A simple method to extract nonlinear signals in time-resolved spectroscopy
PDF
, A simple method to extract nonlinear signals in time-resolved spectroscopy
Time-resolved spectroscopy such as pump–probe and related techniques is the method of choice to observe molecular processes at the femtosecond timescale. The interpretation in terms of excited particles relies on the perturbative expansion of light–matter interaction. The control of contributing nonlinear orders is, however, difficult: at low excitation intensities the contribution of undesired higher orders of nonlinearity is small but so is the overall signal-to-noise ratio (SNR). At high pump intensities the SNR is improved but higher orders of nonlinearity contribute strongly to the overall signal. In this tutorial, we discuss the recently introduced technique of intensity cycling that solves this long-standing problem. Intensity cycling is a simple procedure in pump–probe type spectroscopy that relies on systematic variation of the pump intensity allowing one to separate the nonlinear orders. The nonlinear signals of different order are constructed from linear combinations of measurements at specific pump intensities. We discuss the new fundamental processes that are now accessible through separated higher-order signals such as multi-particle dynamics and interaction. The method is useful especially in extended excitonic systems such as polymers, where it can extract clean single-excitation dynamics and probe exciton diffusion via exciton–exciton annihilation. We review the fundamental and technical challenges of intensity cycling and introduce the language of double-sided Feynman diagrams providing a systematic theoretical framework to describe the various nonlinear signal contributions. We also discuss the recent developments regarding extension and generalization of intensity cycling to other techniques such as two-dimensional spectroscopy. Since intensity cycling can separate nonlinear orders independent of the sample, the method is applicable to a wide range of scientific questions and provides an exciting new perspective of time-resolved spectroscopy.
The following article is
Open access
Angle-resolved photoionization of molecules
Philipp V Demekhin 2026
J. Phys. B: At. Mol. Opt. Phys.
59
053001
View article
, Angle-resolved photoionization of molecules
PDF
, Angle-resolved photoionization of molecules
This tutorial summarizes the essential theoretical background, underlying the angle-resolved photoelectron spectroscopy of molecules. It reports an analytic derivation of the differential cross section for the one-photon ionization of molecules, as well as further analysis and exemplification of the photoelectron angular distributions in the molecular and laboratory frames of reference. Aiming primarily at nonspecialists, it addresses theoreticians and experimentalists in this rapidly-advancing field of research and provides a brief list of theoretical methodologies for numerical calculations in molecules.
Unveiling ion-impact-induced fragmentation dynamics of atoms, molecules, and clusters using the COLTRIMS reaction microscope
Md Abul Kalam Azad Siddiki
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
052001
View article
, Unveiling ion-impact-induced fragmentation dynamics of atoms, molecules, and clusters using the COLTRIMS reaction microscope
PDF
, Unveiling ion-impact-induced fragmentation dynamics of atoms, molecules, and clusters using the COLTRIMS reaction microscope
Over the past 30 years, cold target recoil ion momentum spectroscopy (COLTRIMS) has emerged as a pivotal technique for investigating atomic and molecular interactions under charged particle impacts. By enabling the coincident detection of all correlated fragments with high momentum resolution, COLTRIMS has expedited detailed investigations of atomic and molecular collision processes such as electron capture, ionization, fragmentation, and energy transfer in various few-body systems. This technique has significantly advanced our understanding of quantum correlations, wavefunction entanglement, and reaction-pathway dynamics in various atomic, molecular, and cluster targets. Further technological advances-such as reaction microscopes, which enable the simultaneous detection of both electrons and ions; high-speed position-sensitive detectors; and sophisticated data analysis methods-have broadened the range of COLTRIMS-based experiments to include more complex systems, such as biomolecules and condensed-phase targets. This review offers a comprehensive overview of the significant discoveries made possible by COLTRIMS in studies involving ion beam impacts, highlights recent technical innovations, and discusses emerging research directions in this field.
The following article is
Open access
Why are atomic and molecular dimers so exciting?
Amine Cassimi
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
042001
View article
, Why are atomic and molecular dimers so exciting?
PDF
, Why are atomic and molecular dimers so exciting?
The large number of experimental and theoretical studies devoted to atomic and molecular van der Waals dimers is here to attest for the strong interest and excitement raised in the scientific community over the past decade. One of their intriguing feature is the ability of the two constituting monomers to interact at incredibly large distances through newly evidenced processes, such as Interatomic Coulombic Decay, due to the transition from closed to open shells upon ionization. Beyond the interest for their intrinsic properties, dimers are also valuable for the large amount of information obtained on the monomers themselves, in particular in the case of collisions with ions. Indeed, one of the first striking findings was that dimers behave as two quasi-independent monomers regarding collision processes. This result triggered a series of experiments highlighting specific properties of atomic and molecular dimers, viewed alternatively as new species or as monomers in a minimal environment. They concern several fields, from electron emission to molecular fragmentation. This review presents the diverse and surprising facets of atomic and molecular dimers uncovered through ion collision experiments over the past fifteen years.
Interaction time of two macroscopic quantum wave packets colliding with a rectangular barrier
Li-Zheng Lv
et al
2025
J. Phys. B: At. Mol. Opt. Phys.
58
193501
View article
, Interaction time of two macroscopic quantum wave packets colliding with a rectangular barrier
PDF
, Interaction time of two macroscopic quantum wave packets colliding with a rectangular barrier
We theoretically study the dynamical process of two macroscopic quantum wave packets colliding with a rectangular barrier. We define an interaction time as the time interval between two instants when the atomic probability reaches its maximum at the center and edges of the barrier, serving as a key quantity to characterize this collision process. The impacts of various barrier parameters and wave packet incident energies on the interaction time are systematically explored. Two interferometry schemes, namely Mach–Zehnder scheme and Hong–Ou–Mandel (HOM) scheme, are proposed to determine the interaction time, and the mappings between the interaction time and the observable quantities of the two schemes are established. Through a comparative analysis of the sensitivity of the observable quantities, it is revealed that the HOM scheme exhibits distinct advantages. This research contributes to the quantitative study of quantum tunneling and matter-wave interference, and it is anticipated that the findings can be experimentally validated.
Optimization of the phase sensitivity through photon-subtraction inside the Mach-Zehnder interferometer
Zhou et al
View accepted manuscript
, Optimization of the phase sensitivity through photon-subtraction inside the Mach-Zehnder interferometer
PDF
, Optimization of the phase sensitivity through photon-subtraction inside the Mach-Zehnder interferometer
We propose a photon subtraction scheme within the Mach-Zehnder interferometer using a coherent state and a squeezed vacuum state as inputs. By systematically comparing intensity detection and homodyne detection methods, we demonstrate that strategically applied photon subtraction (a-mode subtraction) significantly enhances the phase sensitivity of all detection methods. Under this configuration, homodyne detection achieves superior phase sensitivity and loss robustness compared to intensity detection. Remarkably, under 30% photon loss, the system surpasses the Heisenberg limit, enabled by the synergy among the squeezed vacuum state, non-Gaussian operations, and detection optimization. Furthermore, we quantify performance through the quantum Fisher information and the quantum Cramér-Rao bound analyses under both ideal and lossy conditions.
The following article is
Open access
Cloud parameter estimation for interacting BEC after time-of-flight
Andersen et al
View accepted manuscript
, Cloud parameter estimation for interacting BEC after time-of-flight
PDF
, Cloud parameter estimation for interacting BEC after time-of-flight
Experiments on Bose-Einstein condensates at finite temperature typically extract the system parameters, such as temperature, atom number, and condensed fraction from time-of-flight images taken after a free expansion time. This paper systematically examines the effect of repulsive interactions between the condensed and thermal atoms in partially condensed clouds on the expansion profile of the thermal cloud. An analytical expression for the expansion can be obtained only if the interactions between the Bose-Einstein condensate and thermal atoms are neglected, resulting in a Bose-enhanced distribution for the thermal component. Here, the deformation of the cloud due to interactions and the effects on estimated parameters are investigated by simulating the expansion using a ballistic approximation. By fitting the simulated expansion profiles with a Bose-enhanced distribution, the errors of using such a fit are estimated, and the results are explained phenomenologically. The simulation was also used as a fitting function for experimental data, showing better agreement of the extracted condensed fraction with the semi-ideal model than results from a Bose-enhanced fit.
Dynamic optical field modulation and biological microparticle trapping using a dual-band wavelength-selective metalens
Guo et al
View accepted manuscript
, Dynamic optical field modulation and biological microparticle trapping using a dual-band wavelength-selective metalens
PDF
, Dynamic optical field modulation and biological microparticle trapping using a dual-band wavelength-selective metalens
Wavelength-selective metasurfaces provide a compact route to tunable optical field control, yet achieving high efficiency and versatile beam shaping at multiple wavelengths remains challenging. We demonstrate a dual-band metalens that switches between a tightly focused Gaussian beam at 1064 nm and a localized hollow beam at 960 nm solely through wavelength tuning, without any mechanical adjustment. Fabricated from TiO₂ nanopillars on a SiO₂ substrate, the device achieves >80% transmission and near-diffraction-limited performance, yielding a 0.56 μm lateral FWHM and a 0.61 μm dark core. Full-wave simulations and optical-force analysis demonstrate that the Gaussian mode enables efficient trapping of high-refractive-index cells, while the hollow mode creates a dark potential well suitable for noninvasive confinement of fragile or low-index biological particles. Compact, integrable, and wavelength-programmable, this lens establishes a versatile platform for dynamic bio-optical manipulation with promising applications in optical trapping, single-cell studies, and lab-on-chip photonics.
Spatiotemporal scales of dynamical quantum phase transitions in the Bose-Hubbard model
Li et al
View accepted manuscript
, Spatiotemporal scales of dynamical quantum phase transitions in the Bose-Hubbard model
PDF
, Spatiotemporal scales of dynamical quantum phase transitions in the Bose-Hubbard model
We investigate the spatial and temporal scales of dynamical quantum phase transitions in the one-dimensional Bose-Hubbard model in the strong interaction limit. Using Jordan-Wigner transformation, we obtain the time-dependent wavefunction and therefore the subsystem Loschmidt echo, and systematically investigate how its properties vary with subsystem size. It is found that when the subsystem is sufficiently large, it exhibits logarithmic divergence identical to that of the full system Loschmidt echo, yielding a critical exponent of zero. We also obtain the required subsystem size and temporal resolution for detecting dynamical quantum phase transitions using the subsystem Loschmidt echo. It is expected that the present results provide a reliable foundation for further experimental investigations.
Fragmentation dynamics of CHF
3+
induced by slow Ar
4+
ions
Singh et al
View accepted manuscript
, Fragmentation dynamics of CHF33+ induced by slow Ar4+ ions
PDF
, Fragmentation dynamics of CHF33+ induced by slow Ar4+ ions
The fragmentation dynamics of CHF
3+
ions produced in slow collisions with Ar
4+
projectile velocity (v = 0.49 a.u.) is investigated using cold-target recoil ion momentum spectroscopy. Five distinct fragmentation pathways are observed, including an incomplete three-body breakup, a complete three-body breakup, and three incomplete four-body dissociation channels. The mechanisms of complete and incomplete three-body fragmentation are analyzed using a Dalitz plot and a Newton diagram, which reveal a signature of sequential dissociation. For the incomplete four-body channels, projected three-dimensional Newton diagrams are employed, allowing for the identification of the underlying stepwise breakup sequence despite the presence of an undetected neutral fragment. For selected channels, potential energy curves of the intermediate ions are calculated to support the sequential behavior inferred from the experimental observations. For all channels, the measured kinetic-energy-release distributions are interpreted within a classical Coulomb-explosion model to understand the underlying charge distribution at the moment of breakup. In addition, the relative yields of multi-electron capture processes are evaluated and analyzed within the framework of the extended classical over-the-barrier (ECOB) model.
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Cloud parameter estimation for interacting BEC after time-of-flight
Rasmus Malthe Fiil Andersen
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
View article
, Cloud parameter estimation for interacting BEC after time-of-flight
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, Cloud parameter estimation for interacting BEC after time-of-flight
Experiments on Bose-Einstein condensates at finite temperature typically extract the system parameters, such as temperature, atom number, and condensed fraction from time-of-flight images taken after a free expansion time. This paper systematically examines the effect of repulsive interactions between the condensed and thermal atoms in partially condensed clouds on the expansion profile of the thermal cloud. An analytical expression for the expansion can be obtained only if the interactions between the Bose-Einstein condensate and thermal atoms are neglected, resulting in a Bose-enhanced distribution for the thermal component. Here, the deformation of the cloud due to interactions and the effects on estimated parameters are investigated by simulating the expansion using a ballistic approximation. By fitting the simulated expansion profiles with a Bose-enhanced distribution, the errors of using such a fit are estimated, and the results are explained phenomenologically. The simulation was also used as a fitting function for experimental data, showing better agreement of the extracted condensed fraction with the semi-ideal model than results from a Bose-enhanced fit.
The following article is
Open access
Accurate two-band tight-binding Hamiltonians for hexagonal two-dimensional materials for strong-field physics
Ofer Neufeld 2026
J. Phys. B: At. Mol. Opt. Phys.
View article
, Accurate two-band tight-binding Hamiltonians for hexagonal two-dimensional materials for strong-field physics
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, Accurate two-band tight-binding Hamiltonians for hexagonal two-dimensional materials for strong-field physics
Two-dimensional hexagonal materials are promising for a variety of applications ranging from valleytronics, spin-current sources, topology, and more. They are recently extensively studied for high-field nonlinear phenomena including Floquet physics, lightwave-driven photogalvanic currents, and high harmonic generation (HHG). For strong-field phenomena, which are typically induced by off-resonant intense driving lasers, two-band tight-binding (TB) descriptions of the system are highly popular because they provide a combination of computational efficiency and accuracy. They are especially appealing since they yield continuous analytic expressions for the band energies and dipole matrix elements, avoiding issues with gauge freedom that can arise in more complex ab-initio theory. However, implementations commonly utilize only up to 2nd nearest-neighbor (NN) terms, which can produce qualitatively wrong band structures in vast regions of the Brillouin zone (BZ). While this approximation is valid for low energy excitations near K/K’, in strong-field conditions it can lead to wrong physical behavior. Here we develop accurate two-band TB Hamiltonians for hexagonal monolayers with up to 14 NN terms that are fitted to ab-initio bands in various systems (graphene, hexagonal-Boron-Nitride, WS2, WSe2, WTe2, MoS2, MoSe2, MoTe2), and reproduce the band structure across the entire BZ, including in regions with inverted curvature near Γ. We employ these models in semi-conductor Bloch equations simulations of HHG, showing that the angular-dependence of HHG yields substantially differs if choosing the full model, or a 2nd-order TB model that correctly captures bands only near K/K’. Our work provides accessible model parameters and analytic expressions for a variety of systems, which should facilitate accurate and efficient simulations of strong-field phenomena in two-dimensional solids. It should also motivate more careful assessment of HHG features before applying various HHG spectroscopy techniques.
The following article is
Open access
Inelastic momentum transfer cross-sections from inelastic differential cross-sections for electron-impact excitation in helium
R J Carman
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
075202
View article
, Inelastic momentum transfer cross-sections from inelastic differential cross-sections for electron-impact excitation in helium
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, Inelastic momentum transfer cross-sections from inelastic differential cross-sections for electron-impact excitation in helium
The inelastic momentum transfer (MT) cross-sections associated with electron-impact excitation of ground-state atomic and molecular species are important for improved accuracy in modelling electron transport in plasmas. In this paper, state-specific inelastic MT cross-sections have been evaluated for electron impact excitation to nine low-lying energy states of helium (2s
1,3
S, 2p
1,3
P, 3s
S, 3p
1,3
P, 3d
1,3
D). This task is dependent on the availability of the underlying inelastic differential cross-sections. These have been calculated theoretically using the relativistic distorted wave (RDW) method, suitable for use at higher electron energies. To our knowledge, this is the first time inelastic MT cross-sections have been evaluated for individual excited states of helium with continuous coverage over a broad range of incident electron energies up to
= 5 keV. Our results are compared to experimentally derived values, and to other theoretical estimates, as are available from the literature. The results confirm that the post collision electron scattering is both energy and He* state dependent. Our RDW results for energies up to 5 keV, together with selected data from 19 other theoretical and experimental studies for energies up to at most 500 eV, have been regression fitted to a general analytical expression, for easy adoption into numerical modelling studies of plasmas.
The following article is
Open access
Measurements of absolute cross sections from excited states via double resonance ion-imaging mass spectrometry: the
autoionizing Rydberg states of argon
Haw-Wei Lin
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
075001
View article
, Measurements of absolute cross sections from excited states via double resonance ion-imaging mass spectrometry: the autoionizing Rydberg states of argon
PDF
, Measurements of absolute cross sections from excited states via double resonance ion-imaging mass spectrometry: the autoionizing Rydberg states of argon
We demonstrate measurements of absolute cross sections from excited states via a double resonance scheme in an ion-imaging mass spectrometer. The method is applied to determine photoexcitation (PE) cross sections of the transition from metastable argon (Ar*) in the
state to the
or
Autoionizing Rydberg States (ARS) of Ar, whose lineshapes and cross sections are sensitive probes for high-level electronic structure theory. The Ar* atoms are generated via electron impact excitation in a pulsed supersonic molecular beam, and a subsequent
in situ
one-photon transition excites the Ar* atoms to the
and
ARS resonances that rapidly evolve into Ar
ions. The lineshapes of the PE spectra of the two ARS of Ar are in excellent agreement with published experimental spectra and high-level
ab initio
calculations. However, the measured absolute cross sections are systematically larger than the theoretical predictions by factors of 2–3, providing new benchmarks to constrain many-electron correlations, core polarization potential, and s-d mixing interactions in electronic structure theory.
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Photoelectric effect of helonium by an arbitrarily polarized XUV laser pulse
H B Ambalampitiya
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
075101
View article
, Photoelectric effect of helonium by an arbitrarily polarized XUV laser pulse
PDF
, Photoelectric effect of helonium by an arbitrarily polarized XUV laser pulse
By means of quantum mechanical calculations, we investigate the Einstein’s photoelectric effect in helonium (HeH
) molecule driven by an arbitrarily polarized XUV pulse of light. To examine the impact of the asymmetric initial electron distribution of the bound state on the photoelectron momentum distributions (PMDs) and the probability current densities (PCDs), we perform a comparative study for fixed-in-space H
or HeH
molecule, whose highest-occupied molecular orbital is symmetric or asymmetric. We find that the same pattern occurs in the PMD and PCD, with great sensitivities to the initial orbital symmetry, molecular orientation and light polarization state. Our simulations thus allow to watch the PMD arise asymptotically in the shape of the coordinate space PCD. In particular, when the light travels perpendicularly to the fixed-in-space H
molecule, a dipole is formed in the distributions for linear polarization (LP), while a yin-yanglike pattern exhibiting dichroism is created for circular polarization (CP). On the contrary, for aligned HeH
a LP pulse drives a large monopole, while a CP pulse transforms the distributions from yin-yanglike patterns to peculiar lung-like patterns including dichroism.
The following article is
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Finite size effects for interacting bosons on small ring lattices
Jian Jun Liu and Kunal K Das 2026
J. Phys. B: At. Mol. Opt. Phys.
59
065301
View article
, Finite size effects for interacting bosons on small ring lattices
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, Finite size effects for interacting bosons on small ring lattices
We study the stationary properties of interacting ultracold bosons in a small one dimensional ring-shaped lattices within a Bose–Hubbard model using finite density matrix renormalization group. Small system size highlights the impact of the periodic boundary condition on the phase transition boundaries and the density–density correlation. Heat maps, as a function of chemical potential and hopping coupling, of differential expectations with respect to the ground and the excited states of energy, entropy and particle number, display a oscillatory stripe pattern that follow the trend of the phase boundaries. These features progressively diminish with system size, and are qualitatively independent of the boundary condition. A mean field analysis demonstrates that the striping is a finite size effect. The momentum distribution as a function of a phase on the hopping potential displays flux quantization effects of the non-trivial topology.
The following article is
Open access
Twisted electron collisions enhance the production of circular Rydberg states
H S Parker
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
065201
View article
, Twisted electron collisions enhance the production of circular Rydberg states
PDF
, Twisted electron collisions enhance the production of circular Rydberg states
Circular Rydberg states offer advantages for quantum information and quantum simulation platforms due to their long lifetimes and strong dipole–dipole interactions. Unfortunately, current techniques for the production of these states remain technically challenging. Here we investigate the ability of twisted electron collisions to produce circular Rydberg states. Twisted electrons carry quantized orbital angular momentum (OAM) that can be transferred to the electronic state of the atom, potentially providing an efficient means to generate circular Rydberg states. Using a fully quantum mechanical framework, we compute total excitation cross sections for circular Rydberg states of hydrogen, lithium, rubidium, and cesium targets using Bessel electron beams. Our models account for the full Bessel-beam structure of the incident electron and incorporate macroscopic target effects to model experimentally-relevant conditions. Our results show that twisted electrons with large opening angles produce significant enhancements in the excitation probability relative to plane-wave electrons, particularly for large opening angles and low energies. We trace this enhancement to contributions from projectiles with large values of OAM. These findings demonstrate that twisted-electron excitation may provide a feasible and potentially advantageous pathway for generating circular Rydberg states.
The following article is
Open access
A simple method to extract nonlinear signals in time-resolved spectroscopy
Julian Lüttig and Pavel Malý 2026
J. Phys. B: At. Mol. Opt. Phys.
59
063001
View article
, A simple method to extract nonlinear signals in time-resolved spectroscopy
PDF
, A simple method to extract nonlinear signals in time-resolved spectroscopy
Time-resolved spectroscopy such as pump–probe and related techniques is the method of choice to observe molecular processes at the femtosecond timescale. The interpretation in terms of excited particles relies on the perturbative expansion of light–matter interaction. The control of contributing nonlinear orders is, however, difficult: at low excitation intensities the contribution of undesired higher orders of nonlinearity is small but so is the overall signal-to-noise ratio (SNR). At high pump intensities the SNR is improved but higher orders of nonlinearity contribute strongly to the overall signal. In this tutorial, we discuss the recently introduced technique of intensity cycling that solves this long-standing problem. Intensity cycling is a simple procedure in pump–probe type spectroscopy that relies on systematic variation of the pump intensity allowing one to separate the nonlinear orders. The nonlinear signals of different order are constructed from linear combinations of measurements at specific pump intensities. We discuss the new fundamental processes that are now accessible through separated higher-order signals such as multi-particle dynamics and interaction. The method is useful especially in extended excitonic systems such as polymers, where it can extract clean single-excitation dynamics and probe exciton diffusion via exciton–exciton annihilation. We review the fundamental and technical challenges of intensity cycling and introduce the language of double-sided Feynman diagrams providing a systematic theoretical framework to describe the various nonlinear signal contributions. We also discuss the recent developments regarding extension and generalization of intensity cycling to other techniques such as two-dimensional spectroscopy. Since intensity cycling can separate nonlinear orders independent of the sample, the method is applicable to a wide range of scientific questions and provides an exciting new perspective of time-resolved spectroscopy.
The following article is
Open access
Angle-resolved photoionization of molecules
Philipp V Demekhin 2026
J. Phys. B: At. Mol. Opt. Phys.
59
053001
View article
, Angle-resolved photoionization of molecules
PDF
, Angle-resolved photoionization of molecules
This tutorial summarizes the essential theoretical background, underlying the angle-resolved photoelectron spectroscopy of molecules. It reports an analytic derivation of the differential cross section for the one-photon ionization of molecules, as well as further analysis and exemplification of the photoelectron angular distributions in the molecular and laboratory frames of reference. Aiming primarily at nonspecialists, it addresses theoreticians and experimentalists in this rapidly-advancing field of research and provides a brief list of theoretical methodologies for numerical calculations in molecules.
The following article is
Open access
Zinc K
ab initio
diagram and satellite transitions
P H Dong
et al
2026
J. Phys. B: At. Mol. Opt. Phys.
59
045002
View article
, Zinc Kβab initio diagram and satellite transitions
PDF
, Zinc Kβab initio diagram and satellite transitions
Anomalies in the characteristic x-ray spectra of 3
transition metals, particularly in lineshape, linewidth, and intensity ratios, have long motivated detailed investigation. We present the first accurate
ab initio
study of the zinc K
spectrum, using multiconfiguration Dirac–Hartree–Fock. We predict the zinc K
spectrum, including the K
diagram doublet together with the dominant satellite transition manifolds for the first time, from
, and
single shake-off, as well as
double shake-off. Such features cannot be resolved by experiment as proven by the literature over several decades. We investigate two novel active space approaches. New convergence metrics are questioned and assessed for energy eigenvalues, gauge ratios
, transition
coefficients, and a newly developed Σ metric. We achieve energy eigenvalue convergence within 0.03 eV, gauge ratios
within 0.6%, convergence of transition
coefficients within 0.03% to 0.23%, and convergence of the Σ-metric to within 0.1% to 6.1%.
Ab initio
shake probabilities are used to quantify satellite contributions to experiment for the first time for zinc. Sequential inclusion of satellite components was evaluated in comparison with the most accurate data available, showing that all dominant shake transitions are required for an accurate description. Incorporating these satellites yields excellent agreement with experiment.
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Rydberg atom quantum technologies
C S Adams
et al
2020
J. Phys. B: At. Mol. Opt. Phys.
53
012002
View article
, Rydberg atom quantum technologies
PDF
, Rydberg atom quantum technologies
This topical review addresses how Rydberg atoms can serve as building blocks for emerging quantum technologies. Whereas the fabrication of large numbers of artificial quantum systems with the uniformity required for the most attractive applications is difficult if not impossible, atoms provide stable quantum systems which, for the same species and isotope, are all identical. Whilst atomic ground states provide scalable quantum objects, their applications are limited by the range over which their properties can be varied. In contrast, Rydberg atoms offer strong and controllable atomic interactions that can be tuned by selecting states with different principal quantum number or orbital angular momentum. In addition Rydberg atoms are comparatively long-lived, and the large number of available energy levels and their separations allow coupling to electromagnetic fields spanning over 6 orders of magnitude in frequency. These features make Rydberg atoms highly desirable for developing new quantum technologies. After giving a brief introduction to how the properties of Rydberg atoms can be tuned, we give several examples of current areas where the unique advantages of Rydberg atom systems are being exploited to enable new applications in quantum computing, electromagnetic field sensing, and quantum optics.
Thermalization and prethermalization in isolated quantum systems: a theoretical overview
Takashi Mori
et al
2018
J. Phys. B: At. Mol. Opt. Phys.
51
112001
View article
, Thermalization and prethermalization in isolated quantum systems: a theoretical overview
PDF
, Thermalization and prethermalization in isolated quantum systems: a theoretical overview
The approach to thermal equilibrium, or thermalization, in isolated quantum systems is among the most fundamental problems in statistical physics. Recent theoretical studies have revealed that thermalization in isolated quantum systems has several remarkable features, which emerge from quantum entanglement and are quite distinct from those in classical systems. Experimentally, well isolated and highly controllable ultracold quantum gases offer an ideal testbed to study the nonequilibrium dynamics in isolated quantum systems, promoting intensive recent theoretical endeavors on this fundamental subject. Besides thermalization, many isolated quantum systems show intriguing behavior in relaxation processes, especially prethermalization. Prethermalization occurs when there is a clear separation of relevant time scales and has several different physical origins depending on individual systems. In this review, we overview theoretical approaches to the problems of thermalization and prethermalization.
Quantum computing with atomic qubits and Rydberg interactions: progress and challenges
M Saffman 2016
J. Phys. B: At. Mol. Opt. Phys.
49
202001
View article
, Quantum computing with atomic qubits and Rydberg interactions: progress and challenges
PDF
, Quantum computing with atomic qubits and Rydberg interactions: progress and challenges
We present a review of quantum computation with neutral atom qubits. After an overview of architectural options and approaches to preparing large qubit arrays we examine Rydberg mediated gate protocols and fidelity for two- and multi-qubit interactions. Quantum simulation and Rydberg dressing are alternatives to circuit based quantum computing for exploring many body quantum dynamics. We review the properties of the dressing interaction and provide a quantitative figure of merit for the complexity of the coherent dynamics that can be accessed with dressing. We conclude with a summary of the current status and an outlook for future progress.
The following article is
Open access
Atom based RF electric field sensing
Haoquan Fan
et al
2015
J. Phys. B: At. Mol. Opt. Phys.
48
202001
View article
, Atom based RF electric field sensing
PDF
, Atom based RF electric field sensing
Atom-based measurements of length, time, gravity, inertial forces and electromagnetic fields are receiving increasing attention. Atoms possess properties that suggest clear advantages as self calibrating platforms for measurements of these quantities. In this review, we describe work on a new method for measuring radio frequency (RF) electric fields based on quantum interference using either Cs or Rb atoms contained in a dielectric vapor cell. Using a bright resonance prepared within an electromagnetically induced transparency window it is possible to achieve high sensitivities, <1
V cm
−1
Hz
−1/2
, and detect small RF electric fields
V cm
−1
with a modest setup. Some of the limitations of the sensitivity are addressed in the review. The method can be used to image RF electric fields and can be adapted to measure the vector electric field amplitude. Extensions of Rydberg atom-based electrometry for frequencies up to the terahertz regime are described.
The following article is
Open access
Advances in attosecond science
Francesca Calegari
et al
2016
J. Phys. B: At. Mol. Opt. Phys.
49
062001
View article
, Advances in attosecond science
PDF
, Advances in attosecond science
Attosecond science offers formidable tools for the investigation of electronic processes at the heart of important physical processes in atomic, molecular and solid-state physics. In the last 15 years impressive advances have been obtained from both the experimental and theoretical points of view. Attosecond pulses, in the form of isolated pulses or of trains of pulses, are now routinely available in various laboratories. In this review recent advances in attosecond science are reported and important applications are discussed. After a brief presentation of various techniques that can be employed for the generation and diagnosis of sub-femtosecond pulses, various applications are reported in atomic, molecular and condensed-matter physics.
Above-threshold ionization by few-cycle pulses
D B Milošević
et al
2006
J. Phys. B: At. Mol. Opt. Phys.
39
R203
View article
, Above-threshold ionization by few-cycle pulses
PDF
, Above-threshold ionization by few-cycle pulses
The theoretical description and the experimental methods and results for above-threshold ionization (ATI) by few-cycle pulses are reviewed. A pulse is referred to as a few-cycle pulse if its detailed shape, parametrized by its carrier-envelope phase, affects its interaction with matter. Angular-resolved ATI spectra are analysed with the customary strong-field approximation (SFA) as well as the numerical solution of the time-dependent Schrödinger equation (TDSE). After a general discussion of the characteristics and the description of few-cycle pulses, the behaviour of the ATI spectrum under spatial inversion is related to the shape of the laser field. The ATI spectrum both for the direct and for the rescattered electrons in the context of the SFA is evaluated by numerical integration and by the method of steepest descent (saddle-point integration), and the results are compared. The saddle-point method is modified to avoid the singularity of the dipole transition matrix element at the steepest-descent times. With the help of the saddle-point method and its classical limit, namely the simple-man model, the various features of the ATI spectrum, their behaviour under inversion, the cut-offs and the presence or absence of ATI peaks are analysed as a function of the carrier-envelope phase of the few-cycle laser field. All features observed in the spectra can be explained in terms of a few quantum orbits and their superposition. The validity of the SFA and the concept of quantum orbits are established by comparing the ATI spectra with those obtained numerically from the
ab initio
solution of the TDSE.
Empirical formula for static field ionization rates of atoms and molecules by lasers in the barrier-suppression regime
X M Tong and C D Lin 2005
J. Phys. B: At. Mol. Opt. Phys.
38
2593
View article
, Empirical formula for static field ionization rates of atoms and molecules by lasers in the barrier-suppression regime
PDF
, Empirical formula for static field ionization rates of atoms and molecules by lasers in the barrier-suppression regime
We propose an empirical formula for the static field ionization rates of atoms and molecules by extending the well-known analytical tunnelling ionization rates to the barrier-suppression regime. The validity of this formula is checked against ionization rates calculated from solving the Schrödinger equation for a number of atoms and ions. The empirical formula retains the simplicity of the original tunnelling ionization rate expression but can be used to calculate the ionization rates of atoms and molecules by lasers at high intensities.
Discrete optics in femtosecond-laser-written photonic structures
Alexander Szameit and Stefan Nolte 2010
J. Phys. B: At. Mol. Opt. Phys.
43
163001
View article
, Discrete optics in femtosecond-laser-written photonic structures
PDF
, Discrete optics in femtosecond-laser-written photonic structures
Over the last few years arrays of evanescently coupled waveguides have been brought into focus as a particular representation of functionalized optical materials, in which the dispersion and diffraction of propagating light can be specifically tuned. Moreover, it turns out that the light evolution in these systems shares fundamental similarities to the quantum evolution of particle wavefunctions, so that waveguide arrays can act as a model system for emulating quantum mechanics. Recently, a novel technique was developed with which waveguides can be directly ‘written’ into various optical bulk materials using femtosecond laser pulses, which allows for the realization of a variety of innovative concepts which are not feasible using other fabrication methods. The aim of this tutorial is to give an introduction to this topic.
Advanced multiconfiguration methods for complex atoms: I. Energies and wave functions
Charlotte Froese Fischer
et al
2016
J. Phys. B: At. Mol. Opt. Phys.
49
182004
View article
, Advanced multiconfiguration methods for complex atoms: I. Energies and wave functions
PDF
, Advanced multiconfiguration methods for complex atoms: I. Energies and wave functions
Multiconfiguration wave function expansions combined with configuration interaction methods are a method of choice for complex atoms where atomic state functions are expanded in a basis of configuration state functions. Combined with a variational method such as the multiconfiguration Hartree–Fock (MCHF) or multiconfiguration Dirac–Hartree–Fock (MCDHF), the associated set of radial functions can be optimized for the levels of interest. The present review updates the variational MCHF theory to include MCDHF, describes the multireference single and double process for generating expansions and the systematic procedure of a computational scheme for monitoring convergence. It focuses on the calculations of energies and wave functions from which other atomic properties can be predicted such as transition rates, hyperfine structures and isotope shifts, for example.
Assessment of Rydberg atoms for wideband electric field sensing
David H Meyer
et al
2020
J. Phys. B: At. Mol. Opt. Phys.
53
034001
View article
, Assessment of Rydberg atoms for wideband electric field sensing
PDF
, Assessment of Rydberg atoms for wideband electric field sensing
Rydberg atoms have attracted significant interest recently as electric field sensors. In order to assess potential applications, detailed understanding of relevant figures of merit is necessary, particularly in relation to other, more mature, sensor technologies. Here we present a quantitative analysis of the Rydberg sensor’s sensitivity to oscillating electric fields with frequencies between 1 kHz and 1 THz. Sensitivity is calculated using a combination of analytical and semi-classical Floquet models. Using these models, optimal sensitivity at arbitrary field frequency is determined. We validate the numeric Floquet model via experimental Rydberg sensor measurements over a range of 1–20 GHz. Using analytical models, we compare with two prominent electric field sensor technologies: electro-optic crystals and dipole antenna-coupled passive electronics.
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1988-present
Journal of Physics B: Atomic, Molecular and Optical Physics
doi: 10.1088/issn.0953-4075
Online ISSN: 1361-6455
Print ISSN: 0953-4075
Journal history
1988-present
Journal of Physics B: Atomic, Molecular and Optical Physics
1968-1987
Journal of Physics B: Atomic and Molecular Physics