Circular Dichroism of RbHe and RbN$_2$ Molecules

TL;DR

This paper investigates how collisions with helium-3 and nitrogen gases affect the circular dichroism of optically pumped rubidium vapor, revealing impacts on transparency and laser power requirements.

Contribution

It provides the first measurements of Rb vapor circular dichroism near the D1 line with buffer gases and explains the results using RbHe potential curves.

Findings

Collisions with buffer gases reduce vapor transparency even when fully polarized.

He results align with RbHe potential curve predictions.

Optical pumping efficiency is affected by spectral profile interactions, increasing laser power needs.

Abstract

We present measurements of the circular dichroism of optically pumped Rb vapor near the D1 resonance line. Collisions with the buffer gases $^3$He and N$_2$ reduce the transparency of the vapor, even when fully polarized. We use two methods to measure this effect, show that the He results can be understood from RbHe potential curves, and show how this effect conspires with the spectral profile of the optical pumping light to increase the laser power demands for optical pumping of very optically thick samples.