Effects of Nitrogen Quenching Gas on Spin-Exchange Optical Pumping of He-3

TL;DR

This paper investigates how nitrogen quenching gas affects the preservation of nuclear spin polarization during spin-exchange optical pumping of helium-3, considering various atomic interactions and relaxation processes.

Contribution

It provides a detailed analysis of nuclear spin conservation during optical pumping, including effects of excited-state hyperfine interactions and collisional relaxation, which were previously neglected.

Findings

Hyperfine interactions influence nuclear spin preservation.

Collisional relaxation impacts polarization efficiency.

Radiation trapping effects are simplified but considered.

Abstract

We consider the degree of conservation of nuclear spin polarization in the process of optical pumping under typical spin-exchange optical pumping conditions. Previous analyses have assumed that negligible nuclear spin precession occurs in the brief periods of time the alkali-metal atoms are in the excited state after absorbing photons and before undergoing quenching collisions with nitrogen molecules. We include excited-state hyperfine interactions, electronic spin relaxation in collisions with He and N_2, spontaneous emission, quenching collisions, and a simplified treatment of radiation trapping.