Multiphoton ionization processes in strong laser

Thesis/Dissertation · Fri Jan 01 00:00:00 EST 1982

OSTI ID:6300850

Krstic, P

Multiphoton ionization of hydrogen in ultrastrong laser fields is studied. The previous calculations of this process yield differing result for the transition rate. We show the relations between them and difficulties with each of them. One difficulty is that the finite spatial and time extent of the laser field has been omitted. It is also found that a laser field, which is sufficiently intense to be labeled ultrastrong, makes the electron move relativistically so that it becomes necessary to use Volkov states to describe the electron in the laser field. The transition rate is obtained, using a CO laser as an example, and it is found that the transition rate rises as the laser intensity rises. This is a consequence of the use of relativistic kinematics and is not true nonrelativistically. We also discuss the multiple peaks observed in the energy spectrum of electrons resulting from multiphoton ionization of atoms by lasers. When the laser intensity is large enough for the ponderomotive force to result in appreciable broading of the peaks we show the shape of the broadened peaks contains useful information. We show that the multiphoton ionization probability as a function of laser intensity can be obtained but that the free-free cross sections, which are in principle also obtainable, are probably not obtainable in practice. Finally, we describe the theory of the absorption of more than minimum numbers of photons needed to ionize an atom by an intense laser. The basic approximation used is that the atom is adiabatically deformed by the laser and an impulsive interaction then results in multiphoton absorption. In our first calculation we allow only one resonant excited state to be included in the adiabatic deformation. In our second we also allow the lowest energy continuum to be included. The two results are then compared.

• Research Organization: City Univ. of New York, NY (USA)
• OSTI ID: 6300850
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
HYDROGEN
PHOTOIONIZATION
CARBON DIOXIDE LASERS
ELECTRON SPECTRA
LASER RADIATION
PHOTON-ATOM COLLISIONS
THEORETICAL DATA
ATOM COLLISIONS
COLLISIONS
DATA
ELECTROMAGNETIC RADIATION
ELEMENTS
GAS LASERS
INFORMATION
IONIZATION
LASERS
NONMETALS
NUMERICAL DATA
PHOTON COLLISIONS
RADIATIONS
SPECTRA
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena