Heteronuclear ionizing collisions between laser-cooled metastable helium atoms

We have investigated cold ionizing heteronuclear collisions in dilute mixtures of metastable (2 S13) He3 and He4 atoms, extending our previous work on the analogous homonuclear collisions [R. J. W. Stas, Phys. Rev. A 73, 032713 (2006)]. A simple theoretical model of such collisions enables us to calculate the heteronuclear ionization rate coefficient, for our quasiunpolarized gas, in the absence of resonant light (T=1.2 mK): K34 (th) =2.4× 10-10 cm3 s. This calculation is supported by a measurement of K34 using magneto-optically trapped mixtures containing about 1× 108 atoms of each species, K34 (exp) =2.5(8)× 10-10 cm3 s. Theory and experiment show good agreement. © 2007 The American Physical Society