Low energy elastic scattering of hydrogen, deuterium and tritium on helium isotopes

TL;DR

This paper calculates energy-dependent elastic scattering cross sections of hydrogen isotopes on helium isotopes, highlighting near-threshold resonances and their implications for atomic physics experiments.

Contribution

It provides new detailed calculations of scattering cross sections for H, D, T on helium isotopes across a broad temperature range, including resonance effects.

Findings

Tritium-helium cross sections are enhanced by a near-threshold s-wave bound state.

At high energies, cross sections approach a geometric limit.

Results are relevant for atomic tritium sources and precision spectroscopy.

Abstract

Motivated by the needs of atomic tritium sources for neutrino mass experiments and Doppler-free two-photon 1S-2S spectroscopy in atomic deuterium and tritium, we present calculations of energy-dependent elastic scattering cross sections of hydrogen isotopes (H, D and T) on helium isotopes ($^3$He and $^4$He) in the temperature range 1~mK to 300~K. The tritium-on-helium cross sections are found to be enhanced over their hydrogen-on-helium counterparts by a near-threshold resonant \textit{s}-wave bound state at low energy, similar to one that has been predicted in the triplet T-T system. While the energy-dependent cross sections span a wide range at low energy due to this \textit{s}-wave enhancement, they tend toward a common value at high energy where the scattering becomes effectively geometric in nature.