# Penning collisions between supersonically expanded metastable helium atoms and laser-cooled lithium atoms

## TL;DR

This paper presents an experimental setup combining supersonic metastable helium beams and a magneto-optical trap for ultracold lithium to study Penning ionization, providing new insights into collision processes and temperature probing.

## Contribution

It introduces a novel experimental system and ion detection scheme for studying Penning collisions between metastable helium and ultracold lithium, enabling high-resolution collision analysis.

## Key findings

- Successful detection and analysis of Penning ionization products.
- Demonstration of using Penning collisions to measure lithium cloud temperature.
- Estimation of excitation efficiency of the helium discharge source.

## Abstract

We describe an experimental setup comprised of a discharge source for supersonic beams of metastable helium atoms and a magneto-optical trap (MOT) for ultracold lithium atoms that makes it possible to study Penning ionization and associative ionization processes at high ion count rates. The cationic reaction products are analyzed using a novel ion detection scheme which allows for mass selection, a high ion extraction efficiency and a good collision-energy resolution. The influence of elastic He-Li collisions on the steady-state Li atom number in the MOT is described, and the collision data are used to estimate the excitation efficiency of the discharge source. We also show that Penning collisions can be directly used to probe the temperature of the Li cloud without the need for an additional time-resolved absorption or fluorescence detection system.