|M.Sc Student||Ido Gilary|
|Subject||Photo-Induced Dynamics of Driven Systems in the High|
|Department||Department of Chemistry||Supervisor||Professor Emeritus Moiseyev Nimrod|
In this research we examine atomic and molecular systems, which are subjected to high intensity radiation in the high frequency regime. We study the mechanism for generation of high harmonics in the high frequency regime and examine the transition from high frequency mechanism to low frequency mechanism. This transition involves a transition from dominant contribution of bound-bound interactions in the high frequency regime to predominant bound-continuum interaction in the low-frequency regime. In order to obtain a better view on high frequency behavior of driven systems we develop here a new transformation of the time dependent Schrodinger equation. This transformation leads to an effective potential, which is time independent and depends on the laser frequency as 1/ω making it applicable in the high frequency regime. The advantage of this transformation over the well-known Kramers-Henneberger transformation is the dependence of the effective potential on the field parameters. As stated the effective potential resulting from our transformation depends only on the laser frequency, ω, while the effective potential of the Kramers-Henneberger representation depends also on the maximum field amplitude. The effective potential obtained by the use of our representation resembles the effective potential for a classical particle subjected to rapidly oscillating time dependent field, proposed by Kapitza. We show that a free quantum particle subjected to high frequency radiation can be trapped even when the mean of the oscillations is equal to zero. Such temporary trapping can occur when the particle is in a metastable state of the effective Hamiltonian. We show that at least one resonance state exists when the potential decays sufficiently fast.