We present the results of experiments measuring the sticking probabili
ty for atomic H on bulk superfluid He-4 for H atom temperatures of 0.3
-4.0 mK. Magnetically trapped, evaporatively cooled gases of atomic hy
drogen were used. The atom temperature (T) dependence of the sticking
probability (s(T)) is consistent with the observation of the onset of
universal quantum reflection (s(T) is-proportional-to T1/2). The data
are in reasonable agreement with recent theoretical calculations.