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

摘要

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