Uključivanje nenultog impulsa elektrona u procenu brzine prelaza u Amosov-Delone-Krajnov teoriji za slučaj niskofrekventnog linearno i cirkularno polarizovanog laserskog polja

Abstract

The subject of research of this doctoral dissertation is process of tunnel ionization which represents one way of interacting atomic systems with ultra short laser pulse. In this process electron in atom can be ionized passing through potential barrier which is destroyed by strong laser field. The goals that were set to the author of this dissertation were to expand ADK theory by including additional parameters and consisted of following: 1. Determination of the influence the initial non zero momentum of ejected electrons and ponderomotive potential to estimate the transition rate in the Ammos-Delone-Krainov theory (ADK theory) in the case of linearly and circularly polarized laser field. 2. Determination of energy which has the largest number of ejected electrons in the ionization of atoms. To achieve these goals, we applied the existing knowledge about lasers, polarization fields and chemical elements, and used theoretical analysis and experimental results obtained by ADK theory. For making graphics software package Wolfram Mathematica 8 was used. The text is organized as follows: The first chapter introduced and defined terms such as linear and nonlinear optics, laser pulse and polarization fields. Without much detail it shows different mechanisms of ionization: multiphoton, above threshold ionization, tunnel and barrier suppression ionization, as well as a mechanism of multiple ionization. The theoretical method of quasi classical approximation, which is based on an approach within one part of the system is described quantum mechanically while the other is treated classically was presented. The second chapter provides an approximation of a strong field, and the most important characteristics of the ADK theory. The calculation of the transition rate by solving the timedependent Schrödinger equation and using the Landau Dychne adiabatic approximation with special emphasis on cases when the initial impulse of the ejected electron is zero and non zero is done. In the third chapter the results of the candidate are presented. The influence of non zero the momentum of ionized electrons and ponderomotive potential on the transition rate for the case of linearly and circularly polarized laser field is considered. The behavior of the cross section and the ions yield in dependence of these parameters is shown. The energy which has a largest number of ejected electrons is calculated also.