  Collisions between tightly confined atoms can lead to ionization and hence to
loss of atoms from the trap. We develop second-order perturbation theory for a
tensorial perturbation of a spherically symmetric system and the theory is then
applied to processes mediated by the spin-dipole interaction. Redistribution
and loss mechanisms are studied for the case of spin-polarized metastable
helium atoms and results obtained for the five lowest s states in the trap and
trapping frequencies ranging from 1 kHz to 10 MHz.
