Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Le Journal de Physique Colloques

SOME NEW PERSPECTIVES IN BREMSSTRAHLUNG RESEARCH

A. Maquet, Alain Dubois, Valérie Vëniard

Published Dec 1, 1987• 0 citations
Publisher

Abstract

We report the results of new theoretical calculations of the transition amplitudes and cross-sections for two distinct bremsstrahlung-related processes : i) Stimulated one-photon transitions (Free-Free Transitions) occuning in the course of electron-H atom collisions, in the presence of a strong extemal field. ii) Two-photon Bremsstrahlung, corresponding to the spontaneous emission of two distinct photons in a single electron-atom collision event. The main features of these processes will be outlined and discussed.

DOI
10.1051/jphyscol:19879141

Related papers

Atomic and Free Electrons in a Strong Light Field

Mikhail Vladimirovich Fedorov

This book presents and describes a series of unusual and striking strong-field phenomena concerning atoms and free electrons. Some of these phenomena are: multiphoton stimulated bremsstrahlung, free-electron lasers, wave-packet physics, above-threshold ionization, and strong-field stabilization in Rydberg atoms. The theoretical foundations and causes of the phenomena are described in detail, with all the approximations and derivations discussed. All the known and relevant experiments are described too, and their results are compared with those of the existing theoretical models.An extensive ge

WORLD SCIENTIFIC eBooks•Jan 1, 1998•218 citations

Theoretical studies of Rydberg atom collisions

R.E. Olson

During the last two years, theoretical studies were performed on a variety of topics related to collisions involving Rydberg atoms. Progress was made towards the understanding of ion-Rydberg atom, Rydberg atom-Rydberg atom, and ground state atom-Rydberg atom collisions. Cross sections were calculated for electron capture, ionization, and excitation processes and parametrized in terms of atomic parameters. A strong dc electric field was also incoporated in calculations of electron capture and ionization cross sections for ion-Rydberg atom collisions. The results of this latter investigation indicate the design of a far ir photon detector which is based on the field ionization of Rydberg atoms may be limited by the collision processes. (Author)

Final Report•Nov 28, 1984•0 citations

Laser-induced radiative collisions (review)

Sergei I Yakovlenko

A theory is given of radiative collisions, i.e., of elementary events in which the emission of a photon occurs in the course of a collision. Special attention is paid to radiative collisions stimulated by a laser field. Simple but clear approaches formulated in the forties or fifties are described briefly. This theory applies, in particular, to collisions in a strong electromagnetic field which affect the collision dynamics. Chemical radiative collisions, i.e., chemical reactions stimulated by photons absorbed in the course of a collision, are reviewed. An analysis is made of several recent experiments in which the theoretically predicted effects were observed: these include the radiative-collisional transfer of excitation from atom to atom, nonlinear effects due to the influence of the field on the collision dynamics, and photosubstitution of one of the atoms in a halogen molecule with an inert gas atom.

Soviet Journal of Quantum Electronics•Feb 28, 1978•59 citations

Two-photon transition in a colliding particle system

Pavel A Apanasevich, Alexander P. Nizovtsev

The first analysis is made of stimulated Raman scattering and two-photon absorption (emission) processes resulting in a change in the states of two colliding particles. These processes are caused the by interaction between dipole moments induced as a result of polarization of the particles by the radiation. Equations are derived to describe multiphoton transitions during a collision between two particles in a radiation field. Using the approximation of rectilinear trajectories, expressions are derived and analyzed for the cross section of collisional two-photon transitions in weak and strong fields. It is shown that in fields of ≈103 cgs esu, the cross section of these transitions may reach 10–4 cm2

Soviet Journal of Quantum Electronics•Mar 31, 1979•1 citation

Electron-Photon Coincidence Technique for Atomic Collisions

Mevlüt Doğan, Hüseyin Ali Yalım

A brief review is given on development of electron-photon coincidence studies from electron impact of atoms. The theory of electron-photon correlations is outlined in detail in terms of cross sections of excited atoms and excited state charge clouds. The state of a target atom is determined by the various orientation and alignment parameters and the multipole moments of the excited atom. General considerations, such as coherence effects in impact excitation, the influence of fine and hyperfine structures in correlations are taken into account. The relationship between scattering amplitudes (including their phases) and target parameters is worked out for singlet and doublet transitions.

Afyon Kocatepe Üniversitesi Fen Ve Mühendislik Bilimleri Dergisi•Jun 1, 2003•0 citations

Multiphoton Ionization of Atoms by Two Radiation Fields: Theory and Calculations for Hydrogen

C. Leone, Saverio Bivona, R. Burlon +1 more

An approximate non-perturbative theory of multiphoton ionization of a hydrogen atom by two strong radiation fields is outlined. The special case is then considered for when one of the fields is of low intensity and high frequency and the other field is of high intensity and low frequency. A set of representative calculations has been performed for this case; that is, (a) angular distributions for given numbers of absorbed and emitted low-frequency photons and different geometries; (b) total cross-sections versus the strong-field intensity; (c) angular distributions summed over all the low-frequency photon exchanges, showing a fourfold symmetry in a geometry in which each ionization channel exhibits, instead, only a twofold symmetry; (d) the average energy gained by the ejected electrons. Calculations are performed for a strong low-frequency field of arbitrary polarization. In many respects, the present calculations are expected to complement those of single-field multiphoton ionization. It is hoped that the results of the calculations reported here may prompt systematic measurements also in this new class of processes, as the predictions are well within the state of the art of present multiphoton-ionization experiments.

Journal of Modern Optics•Jul 1, 1989•3 citations
We report the results of new theoretical calculations of the transition amplitudes and cross-sections for two distinct bremsstrahlung-related processes : i) Stimulated one-photon transitions (Free-Free Transitions) occuning in the course of electron-H atom collisions, in the presence of a strong extemal field. ii) Two-photon Bremsstrahlung, corresponding to the spontaneous emission of two distinct photons in a single electron-atom collision event. The main features of these processes will be outlined and discussed.
This book presents and describes a series of unusual and striking strong-field phenomena concerning atoms and free electrons. Some of these phenomena are: multiphoton stimulated bremsstrahlung, free-electron lasers, wave-packet physics, above-threshold ionization, and strong-field stabilization in Rydberg atoms. The theoretical foundations and causes of the phenomena are described in detail, with all the approximations and derivations discussed. All the known and relevant experiments are described too, and their results are compared with those of the existing theoretical models.An extensive ge
During the last two years, theoretical studies were performed on a variety of topics related to collisions involving Rydberg atoms. Progress was made towards the understanding of ion-Rydberg atom, Rydberg atom-Rydberg atom, and ground state atom-Rydberg atom collisions. Cross sections were calculated for electron capture, ionization, and excitation processes and parametrized in terms of atomic parameters. A strong dc electric field was also incoporated in calculations of electron capture and ionization cross sections for ion-Rydberg atom collisions. The results of this latter investigation indicate the design of a far ir photon detector which is based on the field ionization of Rydberg atoms may be limited by the collision processes. (Author)
A theory is given of radiative collisions, i.e., of elementary events in which the emission of a photon occurs in the course of a collision. Special attention is paid to radiative collisions stimulated by a laser field. Simple but clear approaches formulated in the forties or fifties are described briefly. This theory applies, in particular, to collisions in a strong electromagnetic field which affect the collision dynamics. Chemical radiative collisions, i.e., chemical reactions stimulated by photons absorbed in the course of a collision, are reviewed. An analysis is made of several recent experiments in which the theoretically predicted effects were observed: these include the radiative-collisional transfer of excitation from atom to atom, nonlinear effects due to the influence of the field on the collision dynamics, and photosubstitution of one of the atoms in a halogen molecule with an inert gas atom.
The first analysis is made of stimulated Raman scattering and two-photon absorption (emission) processes resulting in a change in the states of two colliding particles. These processes are caused the by interaction between dipole moments induced as a result of polarization of the particles by the radiation. Equations are derived to describe multiphoton transitions during a collision between two particles in a radiation field. Using the approximation of rectilinear trajectories, expressions are derived and analyzed for the cross section of collisional two-photon transitions in weak and strong fields. It is shown that in fields of ≈103 cgs esu, the cross section of these transitions may reach 10–4 cm2
A brief review is given on development of electron-photon coincidence studies from electron impact of atoms. The theory of electron-photon correlations is outlined in detail in terms of cross sections of excited atoms and excited state charge clouds. The state of a target atom is determined by the various orientation and alignment parameters and the multipole moments of the excited atom. General considerations, such as coherence effects in impact excitation, the influence of fine and hyperfine structures in correlations are taken into account. The relationship between scattering amplitudes (including their phases) and target parameters is worked out for singlet and doublet transitions.
An approximate non-perturbative theory of multiphoton ionization of a hydrogen atom by two strong radiation fields is outlined. The special case is then considered for when one of the fields is of low intensity and high frequency and the other field is of high intensity and low frequency. A set of representative calculations has been performed for this case; that is, (a) angular distributions for given numbers of absorbed and emitted low-frequency photons and different geometries; (b) total cross-sections versus the strong-field intensity; (c) angular distributions summed over all the low-frequency photon exchanges, showing a fourfold symmetry in a geometry in which each ionization channel exhibits, instead, only a twofold symmetry; (d) the average energy gained by the ejected electrons. Calculations are performed for a strong low-frequency field of arbitrary polarization. In many respects, the present calculations are expected to complement those of single-field multiphoton ionization. It is hoped that the results of the calculations reported here may prompt systematic measurements also in this new class of processes, as the predictions are well within the state of the art of present multiphoton-ionization experiments.