Direct measurement of fine-structure collisional losses from a Cs magneto-optical trap

Losses from a cesium magneto-optical trap induced by fine-structure changing collisions have been measured directly by counting of fluorescence photons emitted at the ${\mathrm{D}}_1$ resonance line, with the trap lasers operating on the ${\mathrm{D}}_2$ resonance line. The absolute value of the fine-structure loss rate coefficient has been measured and its dependence on the hyperfine state occupation has been explored. These results provide a fundamental test for the theoretical descriptions of excited-state trap losses.