Homonuclear ionizing collisions of laser-cooled metastable helium atoms

TL;DR

This paper combines theoretical modeling and experimental measurements to study ionizing collisions of laser-cooled metastable helium isotopes, revealing insights into quantum statistical effects and collision dynamics.

Contribution

It introduces a unified quantum threshold and spin-conservation model for homonuclear helium collisions, validated by experimental ionization rate measurements.

Findings

Good agreement between theory and experiment

Ionization rates depend on quantum statistical symmetry

Model applies to both He-3 and He-4 isotopes

Abstract

We present a theoretical and experimental investigation of homonuclear ionizing collisions of laser-cooled metastable helium atoms, considering both the fermionic He-3 and bosonic He-4 isotope. The theoretical description combines quantum threshold behavior, Wigner's spin-conservation rule and quantum statistical symmetry requirements in a single-channel model, complementing a more complete close-coupling theory that has been reported for collisions of metastable He-4 atoms. The model is supported with measurements (in the absence of light fields) of ionization rates in magneto-optically trapped samples, that contain about 3*10^8 atoms of a single isotope. The ionization rates are determined from measurements of trap loss due to light-assisted collisions combined with comparative measurements of the ion production rate in the absence and presence of trapping light. Theory and experiment show good agreement.