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

Physical Review A

Theory of laser-induced transitions between autoionizing states of He

H. Bachau, P. Lambropoulos, Robin Shakeshaft

Published Dec 1, 1986• 55 citations
Publisher

Abstract

We present a theory and calculations of transitions between autoionizing states in He. A $^{1}\mathrm{P}$ resonance is assumed excited by a weak source while a strong laser couples it to other autoionizing states. We calculate the total ionization probability, the line shape, and their dependence on the intensity of the laser. Possible experimental verification is also assessed.

DOI
10.1103/physreva.34.4785

Related papers

Laser-induced autoionizing and continuum structures: Line-shape study in the presence of continuum-continuum transitions

Stefano Cavalieri, R. Eramo, Roberto Buffa +1 more

We present a theoretical study of laser-induced autoionization and laser-induced continuum structures, performed with the aim of deriving predictions on the effect of continuum-continuum transitions on the resonance line shape. The model, developed as an extension of models introduced for the description of laser-induced autoionization and laser-induced continuum structures, on one hand, and for above-threshold ionization, on the other hand, provides quantitative predictions. For specific atomic systems, the line shapes of the structures are shown not to be affected by continuum-continuum transitions, in contrast with previously reported results.

Physical Review A•Apr 1, 1995•14 citations

Theoretical study of double-resonance processes in the helium continuum

Alessandro Lami, N. K. Rahman, Pietro Spizzo

The ionization spectrum of the He atom under double-resonance irradiation is studied theoretically. A previously developed theory is extended and adapted to treat this process. The first source (synchrotron) is tuned around the transition from the ground state to the 23sp-- $^{1}P^{o}$ autoionizing state, and the second source (laser) is put in resonance with the transition from 23sp-- $^{1}P^{o}$ to the higher-lying quasibound state 2p3p-- $^{1}P^{e}$ (or 2p4p, 2p5p). Accurate ab initio calculations have been performed to obtain all the necessary parameters. It is found that the single-field ionization spectrum is strongly modified, exhibiting coherent trapping and ac Stark splitting. These results are in consonance with previous model calculations as well as with other ab initio calculations on a different zone of the He continuum. The results show that for the resonances considered these strong effects can be observed at megawatt laser intensities.

Physical Review A•Sep 1, 1989•7 citations

Two-color pump-probe dynamics of transitions between doubly excited states of Helium

Spyros I. Themelis

We discuss the dynamics of the two-photon resonant ionization of helium involving two autoionizing states in the presence of two-color laser fields. The first source is tuned around the transition from the ground state to the 2s2p 1Po autoionizing state, and the second couples the state 2s2p 1Po to the 2p2 1S autoionizing state. The laser coupling between the doubly excited states is shown to lead to modifications of the Beutler-Fano profile and the appearance of an Autler-Townes doublet. This double resonance effect between autoionizing states can be observed at moderate laser intensities easily attainable by currently operated sources.

arXiv:1401.5503•Jan 21, 2014•0 citations

Harmonic generation and multiphoton ionization near an autoionizing resonance

G. Alber, P. Zoller

We theoretically study intensity-saturation effects in resonant harmonic generation and multiphoton ionization. A first laser excites a two-photon resonance which is coupled by a second laser to an autoionizing state. Starting from an effective Hamiltonian for the three resonant atomic states, we derive a set of equations for the density matrix of the gaseous medium and the electromagnetic field within a semiclassical framework. We present and discuss analytical and numerical solutions of these equations which show a variety of line profiles depending critically on the intensities of the incident laser pulses.

Physical Review A•Mar 1, 1983•32 citations

Multiphoton autoionization under strong laser radiation: Three-photon autoionization of strontium as a test case

Young Soon Kim, P. Lambropoulos

A theory of two- and three-photon autoionization is presented for intermediate resonant and non-resonant cases, stressing the laser-intensity effect on the configuration mixing of the final state. Sample calculations are performed for the $5p6s^{1}P$ autoionizing state. The involvement of the $5s5d$ intermediate state includes the effects of ac Stark shifts on the ionization rate, the line shape, and the photoelectron angular distributions.

Physical Review A•Jun 1, 1984•37 citations

Theory of two-photon autoionization of H2

Krishna Rai Dastidar, P. Lambropoulos

We present a model calculation for two-photon autoionization of ${\mathrm{H}}_{2}$ to the $X^{1}\ensuremath{\Sigma}_{g}$ state of ${\mathrm{H}}_{2}^{+}$. The theory is based on a formulation that allows for strong-field effects. It is shown that, as a result of such effects, the autoionization profile will in general exhibit qualitatively new behavior at laser intensities needed for two-photon ionization. The magnitude of these effects depends significantly on the presence of resonance with intermediate states. The notion of autoionization width and $q$ parameter are generalized to include this new behavior. Detailed calculations are reported for intensity effects on the line profile, the role of intermediate resonances, and the separate contribution of the vibrational states of ${\mathrm{H}}_{2}^{+}$ as final states. The feasibility of observation with currently available sources is discussed.

Physical Review A•Jan 1, 1984•21 citations
We present a theory and calculations of transitions between autoionizing states in He. A 1P^{1}\mathrm{P}1P resonance is assumed excited by a weak source while a strong laser couples it to other autoionizing states. We calculate the total ionization probability, the line shape, and their dependence on the intensity of the laser. Possible experimental verification is also assessed.
We present a theoretical study of laser-induced autoionization and laser-induced continuum structures, performed with the aim of deriving predictions on the effect of continuum-continuum transitions on the resonance line shape. The model, developed as an extension of models introduced for the description of laser-induced autoionization and laser-induced continuum structures, on one hand, and for above-threshold ionization, on the other hand, provides quantitative predictions. For specific atomic systems, the line shapes of the structures are shown not to be affected by continuum-continuum transitions, in contrast with previously reported results.
The ionization spectrum of the He atom under double-resonance irradiation is studied theoretically. A previously developed theory is extended and adapted to treat this process. The first source (synchrotron) is tuned around the transition from the ground state to the 23sp-- 1Po^{1}P^{o}1Po autoionizing state, and the second source (laser) is put in resonance with the transition from 23sp-- 1Po^{1}P^{o}1Po to the higher-lying quasibound state 2p3p-- 1Pe^{1}P^{e}1Pe (or 2p4p, 2p5p). Accurate ab initio calculations have been performed to obtain all the necessary parameters. It is found that the single-field ionization spectrum is strongly modified, exhibiting coherent trapping and ac Stark splitting. These results are in consonance with previous model calculations as well as with other ab initio calculations on a different zone of the He continuum. The results show that for the resonances considered these strong effects can be observed at megawatt laser intensities.
We discuss the dynamics of the two-photon resonant ionization of helium involving two autoionizing states in the presence of two-color laser fields. The first source is tuned around the transition from the ground state to the 2s2p 1Po autoionizing state, and the second couples the state 2s2p 1Po to the 2p2 1S autoionizing state. The laser coupling between the doubly excited states is shown to lead to modifications of the Beutler-Fano profile and the appearance of an Autler-Townes doublet. This double resonance effect between autoionizing states can be observed at moderate laser intensities easily attainable by currently operated sources.
We theoretically study intensity-saturation effects in resonant harmonic generation and multiphoton ionization. A first laser excites a two-photon resonance which is coupled by a second laser to an autoionizing state. Starting from an effective Hamiltonian for the three resonant atomic states, we derive a set of equations for the density matrix of the gaseous medium and the electromagnetic field within a semiclassical framework. We present and discuss analytical and numerical solutions of these equations which show a variety of line profiles depending critically on the intensities of the incident laser pulses.
A theory of two- and three-photon autoionization is presented for intermediate resonant and non-resonant cases, stressing the laser-intensity effect on the configuration mixing of the final state. Sample calculations are performed for the 5p6s1P5p6s^{1}P5p6s1P autoionizing state. The involvement of the 5s5d5s5d5s5d intermediate state includes the effects of ac Stark shifts on the ionization rate, the line shape, and the photoelectron angular distributions.
We present a model calculation for two-photon autoionization of H2{\mathrm{H}}_{2}H2​ to the $X^{1}\ensuremath{\Sigma}_{g}$ state of H2+{\mathrm{H}}_{2}^{+}H2+​. The theory is based on a formulation that allows for strong-field effects. It is shown that, as a result of such effects, the autoionization profile will in general exhibit qualitatively new behavior at laser intensities needed for two-photon ionization. The magnitude of these effects depends significantly on the presence of resonance with intermediate states. The notion of autoionization width and qqq parameter are generalized to include this new behavior. Detailed calculations are reported for intensity effects on the line profile, the role of intermediate resonances, and the separate contribution of the vibrational states of H2+{\mathrm{H}}_{2}^{+}H2+​ as final states. The feasibility of observation with currently available sources is discussed.