Photoassociation spectroscopy in Penning ionization reactions at sub-Kelvin temperatures

TL;DR

This paper proposes using photoassociation spectroscopy to better understand Penning ionization reactions at very low temperatures, addressing challenges in characterizing the entrance channel and potential energy surfaces.

Contribution

It introduces a novel spectroscopic method to identify orbiting resonances and probe ionization widths in Penning ionization reactions at sub-Kelvin temperatures.

Findings

Conceptual framework for photoassociation spectroscopy in Penning ionization

Conditions for successful application of the spectroscopy method

Potential to improve understanding of quantum effects in reactive collisions

Abstract

Penning ionization reactions in merged beams with precisely controlled collision energies have been shown to accurately probe quantum mechanical effects in reactive collisions. A complete microscopic understanding of the reaction is, however, faced with two major challenges---the highly excited character of the reaction's entrance channel and the limited precision of even the best state-of-the-art ab initio potential energy surfaces. Here, we suggest photoassociation spectroscopy as a tool to identify the character of orbiting resonances in the entrance channel and probe the ionization width as a function of inter-particle separation. We introduce the basic concept and discuss the general conditions under which this type of spectroscopy will be successful.