Large spin relaxation rates in trapped submerged-shell atoms

TL;DR

This study measures spin relaxation rates in magnetically trapped erbium and thulium atoms, revealing significantly higher rates than in other atoms, due to electrostatic anisotropy, which impacts cooling efficiency.

Contribution

It provides the first quantitative measurements of spin relaxation in submerged-shell atoms, highlighting a dominant relaxation mechanism not previously characterized.

Findings

Spin relaxation rates are 2-3 orders of magnitude higher than in S-state atoms.

Electrostatic anisotropy is identified as the primary relaxation mechanism.

High relaxation rates hinder evaporative cooling of these atoms.

Abstract

Spin relaxation due to atom-atom collisions is measured for magnetically trapped erbium and thulium atoms at a temperature near 500 mK. The rate constants for Er-Er and Tm-Tm collisions are 3.0 times 10^-10 cm^3 s^-1 and 1.1 times 10^-10 cm^3 s^-1, respectively, 2-3 orders of magnitude larger than those observed for highly magnetic S-state atoms. This is strong evidence for an additional, dominant, spin relaxation mechanism, electrostatic anisotropy, in collisions between these "submerged-shell" L > 0 atoms. These large spin relaxation rates imply that evaporative cooling of these atoms in a magnetic trap will be highly inefficient.