Theory of dissociative tunneling ionization

TL;DR

This paper develops a theoretical framework for dissociative tunneling ionization, deriving analytic spectra using the Born-Oppenheimer approximation and comparing them with exact quantum calculations, revealing insights into nuclear wave function imaging and wave behavior.

Contribution

It introduces simplified analytic expressions for ionization spectra using the BO approximation and demonstrates how to image the BO nuclear wave function from spectra.

Findings

Derived analytic expressions for nuclear kinetic energy spectra.

Showed imaging of the BO nuclear wave function is possible.

Compared BO approximation spectra with exact quantum spectra.

Abstract

We present a theoretical study of the dissociative tunneling ionization process. Analytic expressions for the nuclear kinetic energy distribution of the ionization rates are derived. A particularly simple expression for the spectrum is found by using the Born-Oppenheimer (BO) approximation in conjunction with the reflection principle. These spectra are compared to exact non-BO ab initio spectra obtained through model calculations with a quantum mechanical treatment of both the electronic and nuclear degrees freedom. In the regime where the BO approximation is applicable imaging of the BO nuclear wave function is demonstrated to be possible through reverse use of the reflection principle, when accounting appropriately for the electronic ionization rate. A qualitative difference between the exact and BO wave functions in the asymptotic region of large electronic distances is shown. Additionally the behavior of the wave function across the turning line is seen to be reminiscent of light refraction. For weak fields, where the BO approximation does not apply, the weak-field asymptotic theory describes the spectrum accurately.