Alignment-dependent fluorescence emission induced by tunnel ionization of carbon dioxide from lower-lying orbitals

TL;DR

This study measures how the fluorescence emission from tunnel-ionized CO2 molecules depends on their alignment in an intense laser field, providing insights into ionization dynamics of lower orbitals and testing theoretical models.

Contribution

It introduces an all-optical method to probe ionization of lower-lying molecular orbitals and compares experimental results with theoretical models, highlighting their limitations.

Findings

Alignment-dependent fluorescence emission observed

Experimental results compared with SFA and ADK models

Deviations suggest need for improved theories

Abstract

Study on ionization process of molecules in an intense infrared laser field is of paramount interest in strong-field physics and constitutes the foundation of imaging of molecular valence orbitals and attosecond science. We show measurement of alignment-dependent ionization probabilities of the lower-lying orbitals of the molecules by experimentally detecting alignment-dependence of fluorescence emission from tunnel ionized carbon dioxide molecules. The experimental measurements are compared with the theoretical calculations of strong field approximation (SFA) and molecular ADK models. Our results demonstrate the feasibility of an all-optical approach for probing the ionization dynamics of lower-lying orbitals of molecules, which is still difficult to achieve until now by other techniques. Moreover, the deviation between the experimental and theoretical results indicates the incompleteness of current theoretical models for describing strong field ionization of molecules.