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

Collisional & Nonlinear Radiative Processes for Development of Coherent UV & XUV Sources.

C. K. Rhodes

Published Apr 1, 1987• 0 citations
OpenAlex

Abstract

Abstract : Studies of multiphoton ionization of atoms have revealed several unexpected characteristics. The confluence of the experimental evidence leads to the hypothesis that the basic character of the atomic response involves highly organized, coherent motions of entire atomic shells. The important regime, for which the radiative field strength E is greater than an atomic unit, can be viewed in approximate correspondence with the physics of fast atom-atom scattering. This physical picture provides a basis for the expectation that stimulation emission in the x-ray range can be produced by direct highly nonlinear coupling of ultraviolet radiation to atoms. Keywords: Ions, Multiphoton, Photons.

Related papers

Multiphoton Ionization of Atoms

C. K. Rhodes

Studies of multiphoton ionization of atoms have revealed several unexpected characteristics. The confluence of the experimental evidence leads to the hypothesis that the basic character of the atomic response involves highly organized, coherent motions of entire atomic shells. The important regime, for which the radiative field strength is greater than an atomic unit (e/a(2)(0)), can be viewed in approximate correspondence with the physics of fast (approximately 10 MeV per atomic mass unit) atom-atom scattering. This physical picture provides a basis for the expectation that stimulated emission in the x-ray range can be produced by direct, highly nonlinear coupling of ultraviolet radiation to atoms.

Science•Sep 27, 1985•148 citations

Subpicosecond Studies Of Collision-Free Multiple Photon Processes In The Ultraviolet

T. S. Luk, Ulrich A. Johann, Hernan J. Jara +5 more

In recent years a strong interest has developed in the study of the basic coupling mechanisms governing high order multiphoton processes in atomic systems.1 Such interest has been stimulated by the rapid advances in short pulse generation techniques which allow atomic interactions at an intense field strength of the order of atomic field to be studied. Furthermore, good understanding of the highly nonlinear photon interactions is necessary to evaluate the possibility of using multiphoton processes2 as a means to couple energy into excited states emitting in the x-ray region.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Oct 21, 1986•2 citations

XUV coherent Raman superradiance†

Marlan O. Scully, Yuri V. Rostovtsev, Anatoly A. Svidzinsky +1 more

We find that intense short pulses of XUV radiation can be produced by cooperative spontaneous emission from visible or IR laser pulses driving atoms or ions. The process depends on the generation and utilization of atomic coherence as is the case in lasing without inversion. However, the radiation process is not stimulated emission, but is rather cooperative spontaneous emission in the sense of Dicke. More precisely, the many atom mathematics of superradiance has much in common with coherent anti-Stokes Raman scattering. The generation of Raman coherence is considered from the perspectives of multi-photon excitation and breaking of adiabaticity. In particular, we find that the advent of an ultrashort (e.g. single cycle) pulse rewards rethinking of conventional (nanosecond) nonlinear optics with new insights.

Journal of Modern Optics•Nov 10, 2008•14 citations

ATOMS INTERACTING WITH ELECTROMAGNETIC FIELDS, MULTIPHOTON IONIZATION

G. Mainfray

The non linear interaction between an intense laser radiation and atoms leads to ionization through the absorption of N photons from the laser radiation via laser-induced virtual states. The multiphoton ionization rate varies as a function of the laser intensity I as IN. We discuss the two most important effects which govern multiphoton ionization processes : resonance effects and laser-coherence effects. In a moderate laser intensity range (107 - 109 W cm-2) corresponding to the two, three or four-photon ionization of atoms, resonance effects play a dominant role while the photon statistics of the laser radiation are relatively unimportant. On the contrary, in the very high intensity range (1012 - 1013 W cm-2) required to observe large Nth - order ionization processes, coherence effects play a dominant role through N! enhancement in the N-photon ionization rate, while resonance effects are completely damped due to the high laser intensity. We conclude by reviewing the possible applications of multiphoton absorption processes in other fields.

Le Journal de Physique Colloques•Nov 1, 1982•1 citation

Multiphoton Excitation and Ionization of Atoms

Hernan J. Jara, Ulrich A. Johann, T. S. Luk +5 more

It has been conjectured that atomic motions fundamentally different from those presently observed may be driven under extreme conditions of irradiation. Indeed, it has been suggested1-4 that ordered many-electron motions of outer-shell electrons could lead to enhanced rates of coupling from the radiation field to an atom. In order to study the conditions necessary for new atomic responses to occur and to determine the influence of possible damping mechanisms, the properties of ion charge state distributions,5 electron energy spectra,6 and harmonic radiation7 produced by irradiation of atoms with ultra-violet radiation with different pulse lengths, wavelengths, and intensities have been investigated.

Topical Meeting on Multiple Excitations of Atoms•Jan 1, 1986•0 citations

Dynamical Control of the Coherent Forward Scattering of XUV and X-Ray Radiation

T. R. Akhmedzhanov

This work aims at development of new dynamical methods to control a resonant light-matter interaction as well as at their application for producing new sources of coherent intense sub-fs radiation in x-ray range. The dynamical control is based on modulation in time and in space of the parameters of the atomic transition (coupled to the resonant high-frequency field) by means of sufficiently strong off-resonant low-frequency control field. In particular, it may result in efficient transfer of quasi-monochromatic VUV or XUV radiation into ultrashort pulses via its resonant interaction with atomic hydrogen gas or plasma of hydrogen-like ions respectively by means of two different techniques: time and space dependent linear Stark effect or interruption of resonant interaction by the tunneling ionization, as shown in previous works of our group. \n\nIn this thesis, I further develop these ideas and demonstrate their important potential applications. First of all, both techniques are extended to arbitrary (non-hydrogen-like) atomic medium. Furthermore, advanced analytical and numerical solutions describing a process of pulses formation are found and shown to be in excellent agreement with each other. A deep physical analogy between the processes of coherent forward scattering of γ-ray radiation in the vibrated quasi-resonant nuclear absorber and the XUV field propagation in the quasi-resonant atomic medium in the presence of the moderately strong IR field is established. \n\nFinally, the application of the developed techniques for production of intense coherent attosecond sources of soft X-ray radiation, including so-called “water window” range (2.2-4.3nm) (especially promising for dynamical imaging of the proteins in a living cell) is proposed. Two different paths towards production of intense coherent attosecond pulses in a soft X-ray range are suggested: (i) via efficient transformation of the picosecond radiation of the high energy pulses of the existing x-ray plasma lasers into the trains of attosecond pulses in the resonant passive plasma, and (ii) via amplification of the low energy pulses of the existing high harmonic sources in the resonant active plasma of x-ray lasers.

•Feb 27, 2017•0 citations
Abstract : Studies of multiphoton ionization of atoms have revealed several unexpected characteristics. The confluence of the experimental evidence leads to the hypothesis that the basic character of the atomic response involves highly organized, coherent motions of entire atomic shells. The important regime, for which the radiative field strength E is greater than an atomic unit, can be viewed in approximate correspondence with the physics of fast atom-atom scattering. This physical picture provides a basis for the expectation that stimulation emission in the x-ray range can be produced by direct highly nonlinear coupling of ultraviolet radiation to atoms. Keywords: Ions, Multiphoton, Photons.
Studies of multiphoton ionization of atoms have revealed several unexpected characteristics. The confluence of the experimental evidence leads to the hypothesis that the basic character of the atomic response involves highly organized, coherent motions of entire atomic shells. The important regime, for which the radiative field strength is greater than an atomic unit (e/a(2)(0)), can be viewed in approximate correspondence with the physics of fast (approximately 10 MeV per atomic mass unit) atom-atom scattering. This physical picture provides a basis for the expectation that stimulated emission in the x-ray range can be produced by direct, highly nonlinear coupling of ultraviolet radiation to atoms.
In recent years a strong interest has developed in the study of the basic coupling mechanisms governing high order multiphoton processes in atomic systems.1 Such interest has been stimulated by the rapid advances in short pulse generation techniques which allow atomic interactions at an intense field strength of the order of atomic field to be studied. Furthermore, good understanding of the highly nonlinear photon interactions is necessary to evaluate the possibility of using multiphoton processes2 as a means to couple energy into excited states emitting in the x-ray region.
We find that intense short pulses of XUV radiation can be produced by cooperative spontaneous emission from visible or IR laser pulses driving atoms or ions. The process depends on the generation and utilization of atomic coherence as is the case in lasing without inversion. However, the radiation process is not stimulated emission, but is rather cooperative spontaneous emission in the sense of Dicke. More precisely, the many atom mathematics of superradiance has much in common with coherent anti-Stokes Raman scattering. The generation of Raman coherence is considered from the perspectives of multi-photon excitation and breaking of adiabaticity. In particular, we find that the advent of an ultrashort (e.g. single cycle) pulse rewards rethinking of conventional (nanosecond) nonlinear optics with new insights.
The non linear interaction between an intense laser radiation and atoms leads to ionization through the absorption of N photons from the laser radiation via laser-induced virtual states. The multiphoton ionization rate varies as a function of the laser intensity I as IN. We discuss the two most important effects which govern multiphoton ionization processes : resonance effects and laser-coherence effects. In a moderate laser intensity range (107 - 109 W cm-2) corresponding to the two, three or four-photon ionization of atoms, resonance effects play a dominant role while the photon statistics of the laser radiation are relatively unimportant. On the contrary, in the very high intensity range (1012 - 1013 W cm-2) required to observe large Nth - order ionization processes, coherence effects play a dominant role through N! enhancement in the N-photon ionization rate, while resonance effects are completely damped due to the high laser intensity. We conclude by reviewing the possible applications of multiphoton absorption processes in other fields.
It has been conjectured that atomic motions fundamentally different from those presently observed may be driven under extreme conditions of irradiation. Indeed, it has been suggested1-4 that ordered many-electron motions of outer-shell electrons could lead to enhanced rates of coupling from the radiation field to an atom. In order to study the conditions necessary for new atomic responses to occur and to determine the influence of possible damping mechanisms, the properties of ion charge state distributions,5 electron energy spectra,6 and harmonic radiation7 produced by irradiation of atoms with ultra-violet radiation with different pulse lengths, wavelengths, and intensities have been investigated.
This work aims at development of new dynamical methods to control a resonant light-matter interaction as well as at their application for producing new sources of coherent intense sub-fs radiation in x-ray range. The dynamical control is based on modulation in time and in space of the parameters of the atomic transition (coupled to the resonant high-frequency field) by means of sufficiently strong off-resonant low-frequency control field. In particular, it may result in efficient transfer of quasi-monochromatic VUV or XUV radiation into ultrashort pulses via its resonant interaction with atomic hydrogen gas or plasma of hydrogen-like ions respectively by means of two different techniques: time and space dependent linear Stark effect or interruption of resonant interaction by the tunneling ionization, as shown in previous works of our group. \n\nIn this thesis, I further develop these ideas and demonstrate their important potential applications. First of all, both techniques are extended to arbitrary (non-hydrogen-like) atomic medium. Furthermore, advanced analytical and numerical solutions describing a process of pulses formation are found and shown to be in excellent agreement with each other. A deep physical analogy between the processes of coherent forward scattering of γ-ray radiation in the vibrated quasi-resonant nuclear absorber and the XUV field propagation in the quasi-resonant atomic medium in the presence of the moderately strong IR field is established. \n\nFinally, the application of the developed techniques for production of intense coherent attosecond sources of soft X-ray radiation, including so-called “water window” range (2.2-4.3nm) (especially promising for dynamical imaging of the proteins in a living cell) is proposed. Two different paths towards production of intense coherent attosecond pulses in a soft X-ray range are suggested: (i) via efficient transformation of the picosecond radiation of the high energy pulses of the existing x-ray plasma lasers into the trains of attosecond pulses in the resonant passive plasma, and (ii) via amplification of the low energy pulses of the existing high harmonic sources in the resonant active plasma of x-ray lasers.