Getting the elastic scattering length by observing inelastic collisions in ultracold metastable helium atoms

TL;DR

This study measures ion flux in ultracold metastable helium to determine the scattering length, revealing the onset of Bose-Einstein condensation and refining previous estimates with interaction corrections.

Contribution

It provides an improved measurement of the scattering length in metastable helium atoms using ion flux observations during Bose-Einstein condensation.

Findings

Ion flux sharply increases at BEC onset

Refined scattering length value: 11.3 nm

Includes corrections for atomic interactions on critical temperature

Abstract

We report an experiment measuring simultaneously the temperatureand the flux of ions produced by a cloud of triplet metastablehelium atoms at the Bose-Einstein critical temperature. The onsetof condensation is revealed by a sharp increase of the ion fluxduring evaporative cooling. Combining our measurements withprevious measurements of ionization in a pure BEC,we extract an improved value of the scattering length$a=11.3^{+2}_{-1}$ nm. The analysis includes corrections takinginto accountthe effect of atomic interactions on the criticaltemperature, and thus an independent measurement of the scatteringlength would allow a new test of these calculations.