We observe that the Rb-Rb relaxation rate for spin polarized Rb is red
uced by a factor of 3 in magnetic fields of a few kG, even at multiatm
osphere buffer gas pressures. This reduction is proportional to the Rb
density and is independent of buffer gas pressure between 100 and 300
0 Torr. We also report anomalously large relaxation rates below 100 To
rr. Both of these observations are inconsistent with the previously he
ld assumption that the Rb-Rb relaxation arises from sudden binary coll
isions.