Charles Joachain

High-Intensity Laser-Atom Physics

Publisher Summary This chapter illustrates that the development of lasers capable of delivering short pulses of very intense radiation, over a wide frequency range, has led to the discovery of new, nonperturbative multiphoton processes in laser interactions with atomic systems. In this article, we first give a survey of the main properties of multiphoton processes such as the multiphoton ionization of atoms, the emission by atoms of high-order harmonics of the exciting laser light, and laser-assisted electron-atom collisions. It then review the theory of these processes, giving particular attention to ab-initio nonperturbative methods such as the Sturmian-Floquet approach, the R-matrix-Floquet theory, and the numerical integration of the time-dependent Schrodinger equation. The chapter discusses relativistic effects that occur at ultra-high intensities. The chapter concludes by considering possible future developments of high-intensity laser-atom physics.

Photon and electron collisions with atoms and molecules

Excitation of Atoms by Electron Impact: Current Status and Future Prospects K. Bartschat. Electron-Helium Correlation Studies A. Crowe. Ionization of Atoms and Ions by Electron Impact R.H.G. Reid. R-Matrix Theory of Electron-Molecule Collisions L.A. Morgan. Electron Collisions with Molecules on Metal Surfaces J.P. Gauyacq, et al. Recent Measurements of Differential Cross Sections for Electron-Molecule Collisions at Low Energies M. Allan. Dissociative Recombination: New Developments Stimulated by Ion Storage Ring Experiments A. Suzor-Weiner, et al. One and Two-Electron Resonances in Molecular Photoionization R.W. Zurales. Double Photoionization of Helium M. Pont, R. Shakeshaft. Multicolor Photoionization of Atoms with an IR Laser and Its Higher UV Harmonics V. Veniard, et al. Stabilization of Atoms in Ultra-Strong Laser Fields M. Gavrila. Laser Assisted and Laser Produced Scattering J.H. Sanderson, W.R. Newell. R-Matrix-Floquet Theory of Multiphoton Processes M. Dorr. Resonance Effects in Multiphoton Ionization N.J. Kylstra. Multiphoton Processes in a Two-Electron Atom Using a Cray T3D K.T. Taylor, et al. Application of Parallel Computers to Electron Molecule Scattering Calculations N. Sanna, F.A. Gianturco. 7 Additional Articles. Index.

R-Matrix-Floquet Theory of Multiphoton Processes

The R-matrix-Floquet theory1 enables the interaction of intense laser fields with complex atoms and ions to be studied in a fully non-perturbative manner. In particular it has been used to study multiphoton ionization, laser-assisted electron-atom scattering, harmonic generation and multiphoton processes involving two incommensurate frequencies. Taking advantage of R-matrix theory the method is able to represent the atomic structure accurately and so, for example, the role of resonances in the ionization process can be studied in detail. This has permitted a wide range of atoms and negative ions to be considered including H, H-, He, Ne, Ar, Mg, F-, Cl- and Li-. As well as yielding total ionization rates, partial rates and angular distributions the R-matrix-Floquet approach has enabled other phenomena to be considered. Of particular interest here has been the study of laser-induced degenerate states (LIDS) such as those found in Ar2,3. An example of a LIDS process will be considered below.

Atoms, solids, and plasmas in super-intense laser fields

Part 1: Lectures. 1. Ultra-intense lasers and their applications G. Mourou. Atomic and Molecular Physics. 2. Theory of multiphonton ionization of atoms N.J. Kylstra, et al. 3. Experiments of multiphoton dissociation and ionization of molecules H. Rottke. 4. Two-color and sigle-color above threshold ionization P. Agostini. 5. High-order harmonic generation P. Salieres. 6. Cluster in intense laser fields J.W.G. Tisch. 7. Introduction to laser-plasma interaction and its applications S. Atzeni. 8. Experimental study of Petawatt laser produced plasmas M. Key. 9. Relativistic laser plasma interactions J. Meyer-ter-Vehn, et al. 10. Dense ultrafast plasmas J.C. Gauthier. 11. Magnetic fields and solitons in relativistic plasmas F. Pegoraro, et al. Part 2: Seminars. Atomic and Molecular Physics. 12. R-Matrix-floquet theory of two electron atoms in intense laser fields M. Dorr. 13. Intense-field many-body-matrix theory: applications to recoil momentum distribution for laser-induced double ionization F.H.M. Faisal. 14. electrons and ions in relativistic laser fields Y.I. Salamin. 15. the classical and the quantum face of above-threshold ionization G.G. Paulus, H. Walther. 16. Relativistic effects in non-linear atom-laser interactions at ultrahigh intensities V. Veniard. Plasmas 17. Plasmas at solid state density generated by ultra-short laser pulses K. Eidmann. 18.Shock wave experiments and equation of state of dense matter M. Koenig.19.Laser particle acceleration in plasmas J.R. Marques. Part 3: Posters. 20. Elliptic dichroism in angular distributions in free-free transitions in hydrogen A. Cionga, et al. 21. Shock electromagnetic waves resulting from higher harmonics generation in transparent solids V.E. Gruzdev, A Guzdeva. 22. study of fast electron propagation in ultra-intense laser pulse interaction with solid targets using rear side optical self-radiation and reflectivity-based diagnostics J.J. Santos, et al. 23. Demonstration of hybridly pumped soft X-ray laser F. Bortolotto. 24.X-ray emission from laser irradiated structured gold targets T. Desai. 25.Measurement of spectral and angular distribution of hard X-rays from laser produced plasmas and their application S. Dusterer, et al. 26. Equation of state of water in the megabar range E. Henry. 27. XUV interferometry using high order harmonics: application to plasma diagnostics J.F. Hergott. Index.

Eikonal theory of electron- and positron-atom collisions☆

Abstract We review recent developments in the application of eikonal methods to the field of electron and positron collisions with atoms. The foundations of the eikonal approximation are first analyzed within the framework of potential scattering, with particular attention to those aspects of the theory which can be generalized to atomic collision processes. We next discuss various many-body applications of the eikonal method, namely: the Glauber approximation, the eikonal-Born series method, optical model theories, the eikonal distorted wave method and the multistate eikonal approximation. We also analyze eikonal exchange amplitudes. Applications of these methods are then considered, first for the case of elastic scattering and then for various inelastic processes.

Theory of (e,2e) Reactions

The most detailed information presently available about the ionization of atoms by electron impact is obtained by analyzing triple differential cross sections, measured in (e,2e) experiments. In this article a survey is given of recent advances in the theoretical study of these (e,2e) reactions.

Photon emission by ions interacting with short intense laser pulses: beyond the dipole approximation

Abstract : Photon emission by a positive ion exposed to an intense few-cycle Ti:Sapphire laser pulse is studied within the strong field approximation. We find that the magnetic field component of the incident pulse has little effect below 10(exp 17) W sq cm peak intensity. However, for more intense pulses it significantly reduces photon emission and changes the plateau structure of the spectra, as compared to the predictions of the dipole approximation, and leads in certain parts of the spectrum to emission in the form of a single attosecond burst of X-ray photons. Results obtained by solving the time-dependent Schrodinger equation for a two dimensional model of atomic hydrogen interacting with an ultrashort high frequency laser pulse are also given for photon emission in the stabilization regime; for the case studied, the main effect of the pulses magnetic field is to produce a relatively strong emission at the second harmonic frequency.

Atomic hydrogen in a superintense high-frequency field : testing the dipole approximation

We have solved the fully 3-dimensional time-dependent Schrodinger and Pauli equations for an electron bound in a Coulomb potential, interacting with a superintense electromagnetic (laser) field of high frequency. Adiabatic stabilization is observed at high intensities. Corrections to the dipole approximation modify the ionization probability only slightly, up to the maximum intensity considered (2.5 1019 W cm-2).

R-matrix-Floquet theory of multiphoton processes. II. Solution of the asymptotic equations in the velocity gauge

For pt.I see ibid., vol.24, no.4, p.751-90 (1991). A unified R-matrix-Floquet theory of multiphoton ionization and laser-assisted electron-atom collisions for a general atom has been proposed recently by Burke et al. (1990, 1991). The present paper describes two new computational methods for solving the asymptotic equations which occur in the external R-matrix region in the velocity gauge. The first method extends the Light and Walker (1976) propagator approach to include the first derivative coupling term which arises in the velocity gauge. The second method extends the Burke and Schey (1962) asymptotic expansion to include the first derivative coupling terms and the long-range multipole potential terms. These new methods, combined with the solution in the internal R-matrix region, enable the complete solution of the R-matrix-Floquet equations to be obtained. By introducing a small r expansion of the one-electron system in the velocity gauge, numerical results are presented for multiphoton ionization of atomic hydrogen and compared with results obtained using other approaches.

Optical model theory of elastic electron- and positron-argon scattering at intermediate energies

The authors compare two recently proposed ab initio optical model methods and obtain an improved absorption potential for the case of scattering of fast charged particles by heavy atoms. Detailed calculations are performed for elastic scattering of electrons and positrons by argon in the energy region 100 eV-1 keV. The differential cross sections for electron scattering are in excellent agreement with recent absolute measurements. Total cross sections for both electron and positron collisions are also discussed.