Semiclassical complex-time method for tunneling ionization: Molecular suppression and orientational dependence

Authors

Gordon A. Gallup, University of Nebraska-LincolnFollow
Ilya I. Fabrikant, University of Nebraska-LincolnFollow

Date of this Version

2010

Comments

Published in PHYSICAL REVIEW A 81, 033417 (2010). Copyright ©2010 The American Physical Society. Used by permission.

Abstract

We apply a previously developed semiclassical complex time method to the calculation of tunneling ionization of several diatomic molecules and CO₂.We investigate the presence or absence of the molecular suppression effect by calculating ionization rates of N₂ versus Ar, O₂ versus Xe, F₂ versus Ar, and CO versus Kr. Comparisons with other theories, including the molecular-orbital-Ammosov-Delone-Krainov (MO-ADK) model and the strong-field approximation, are given. We also analyze the dependence of the ionization rate on the angle θ_F between the molecular axis and the field direction. The theoretical results agree quite well with experiment for N2 and O2 but give too low a value of the peak angle θ_F for CO₂. Our calculations give small values of the ionization rates for O₂ and CO₂ at θ_F = 0 and 90°, in agreement with experiment. Other calculations, including the MO-ADK model and methods involving a numerical integration of the time-dependent Schrodinger equation, exhibit substantially weaker suppression at these angles.