Spin-velocity correlations of optically pumped atoms

TL;DR

This paper develops efficient theoretical tools to describe the optical pumping of atoms considering arbitrary light directions and collisional effects, with applications to sodium guidestars in adaptive optics.

Contribution

It introduces a novel approach combining spin and velocity relaxation modes with cusp kernels and complex velocity poles for accurate modeling of optical pumping under realistic conditions.

Findings

Theoretical models match experimental data well.

Methods applicable to sodium guidestars at high altitudes.

Enhanced understanding of velocity-selective optical pumping.

Abstract

We present efficient theoretical tools for describing the optical pumping of atoms by light propagating at arbitrary directions with respect to an external magnetic field, at buffer-gas pressures that are small enough for velocity-selective optical pumping (VSOP) but large enough to cause substantial collisional relaxation of the velocities and the spin. These are the conditions for the sodium atoms at an altitude of about 100 km that are used as guidestars for adaptive optics in modern ground-based telescopes to correct for aberrations due to atmospheric turbulence. We use spin and velocity relaxation modes to describe the distribution of atoms in spin space (including both populations and coherences) and velocity space. Cusp kernels are used to describe velocity-changing collisions. Optical pumping operators are represented as a sum of poles in the complex velocity plane. Signals simulated with these methods are in excellent agreement with previous experiments and with preliminary experiments in our laboratory.