Keldysh-type photoionization rate of large polyatomic molecules in the tunneling region
Journal
Physical Review A - Atomic, Molecular, and Optical Physics
Journal Volume
71
Journal Issue
5
Date Issued
2005
Author(s)
Abstract
In this paper, we demonstrate a detailed derivation of general analytical expressions of photoionization rates of spatially aligned large polyatomic molecules in the tunneling photoionization region. First, the molecular Coulomb-corrected Volkov function is derived for determining the continuum state, and the position dependence of the atoms forming the molecule is explicitly included in it. Second, using the molecular Coulomb-corrected Volkov function, a Keldysh-type photoionization rate formula is derived. For this, a linear combination of atomic orbitals will be used for the initial state. The obtained photoionization rate formula shows that the molecular photoionization rate is the sum of the photoionization rates of the individual occupied orbitals of the atoms forming the molecule, which are modified by the position dependence of the atoms, and the quantum interference terms arising from the corresponding occupied orbitals of the constituent identical and different atoms. The formula explicitly indicates that the photoionization rate sensitively depends on the angle between the molecular axis and the polarization vector of the linearly polarized laser field, the internuclear distance, and the atomic ionization potential I by the expression exp(22mIF F). This is a clear indication of the appropriateness of the formulas derived in this work since it is consistent with the experimental and numerical results obtained so far. Using the formula, we show numerical results of photoionization rates of all-trans polyacetylene radicals. In addition, from the formula is directly drawn the conclusion that the photoionization rate corresponding to the quantum interference terms is smaller when the distance between the atoms is longer in the case of laser polarization parallel to the molecular backbone. © 2005 The American Physical Society.
In this paper, we demonstrate a detailed derivation of general analytical expressions of photoionization rates of spatially aligned large polyatomic molecules in the tunneling photoionization region. First, the molecular Coulomb-corrected Volkov function is derived for determining the continuum state, and the position dependence of the atoms forming the molecule is explicitly included in it. Second, using the molecular Coulomb-corrected Volkov function, a Keldysh-type photoionization rate formula is derived. For this, a linear combination of atomic orbitals will be used for the initial state. The obtained photoionization rate formula shows that the molecular photoionization rate is the sum of the photoionization rates of the individual occupied orbitals of the atoms forming the molecule, which are modified by the position dependence of the atoms, and the quantum interference terms arising from the corresponding occupied orbitals of the constituent identical and different atoms. The formula explicitly indicates that the photoionization rate sensitively depends on the angle between the molecular axis and the polarization vector of the linearly polarized laser field, the internuclear distance, and the atomic ionization potential I by the expression exp(22mIF F). This is a clear indication of the appropriateness of the formulas derived in this work since it is consistent with the experimental and numerical results obtained so far. Using the formula, we show numerical results of photoionization rates of all-trans polyacetylene radicals. In addition, from the formula is directly drawn the conclusion that the photoionization rate corresponding to the quantum interference terms is smaller when the distance between the atoms is longer in the case of laser polarization parallel to the molecular backbone. © 2005 The American Physical Society.
Type
journal article