Continuum-continuum dipole transitions in femtosecond-laser-pulse excitation of atomic hydrogen
- Laboratoire de Chimie Physique, Universite Pierre et Marie Curie, 11, Rue Pierre et Marie Curie, F-75231 Paris CEDEX 05, France (FR)
We study in detail the electron energy spectrum produced by the interaction of atomic hydrogen initially in the 2{ital s} state with a femtosecond laser pulse. As a first step, we treat the problem within second-order perturbation theory. For that purpose, we analyze in the first instance the off-diagonal continuum-continuum transition matrix elements and derive asymptotic expressions when both the initial- and final-state energies are very close to the ionization threshold. We also consider the diagonal divergence and extend a recent calculation of Madajczyk and Trippenbach (J. Phys. A 22, 2369 (1989)). By means of a proper analytical regularization of these matrix elements, we show that they may be considered as a distribution, which, in addition to a {delta} function and its first derivative, involves three principal parts. When this distribution is acting on a given function of energy, it is shown that the calculation of these three principal parts may be carried out fully analytically. We then present results for the electron energy spectrum. Various pulse shapes are considered, and a detailed discussion is given on the contribution of the intermediate continuum states to the second-order probability amplitude.
- OSTI ID:
- 7188724
- Journal Information:
- Physical Review, A (General Physics); (USA), Vol. 41:7; ISSN 0556-2791
- Country of Publication:
- United States
- Language:
- English
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HYDROGEN
PHOTON-ATOM COLLISIONS
ELECTRON SPECTRA
ENERGY SPECTRA
EXCITATION
LASER RADIATION
MULTI-PHOTON PROCESSES
PERTURBATION THEORY
PHOTOIONIZATION
PULSED IRRADIATION
ATOM COLLISIONS
COLLISIONS
ELECTROMAGNETIC RADIATION
ELEMENTS
ENERGY-LEVEL TRANSITIONS
IONIZATION
IRRADIATION
NONMETALS
PHOTON COLLISIONS
RADIATIONS
SPECTRA
640302* - Atomic
Molecular & Chemical Physics- Atomic & Molecular Properties & Theory