Theory of evaporative cooling with energy-dependent elastic scattering cross section and application to metastable helium

TL;DR

This paper extends the kinetic theory of evaporative cooling to include energy-dependent elastic scattering cross sections, providing a more accurate model and applying it to metastable helium to determine its scattering length.

Contribution

The paper introduces a modified theory of evaporative cooling that accounts for energy-dependent scattering cross sections and demonstrates its application to metastable helium.

Findings

Estimated scattering length |a| = 10(5) nm for metastable helium

Extended theory accurately describes the transition between low-temperature and unitarity limits

Provides a practical approximation for energy-dependent scattering in cooling models

Abstract

The kinetic theory of evaporative cooling developed by Luiten et al. [Phys. Rev. A 53, 381 (1996)] is extended to include the dependence of the elastic scattering cross section on collision energy. We introduce a simple approximation by which the transition range between the low-temperature limit and the unitarity limit is described as well. Applying the modified theory to our measurements on evaporative cooling of metastable helium we find a scattering length |a| = 10(5) nm.