  We present a theoretical study of the Zeeman relaxation of the magnetically
trappable lowest field seeking state of MnH(^7 \Sigma) in collisions with 3He.
We analyze the collisional Zeeman transition mechanism as a function of the
final diatomic state and its variation as a function of an applied magnetic
field. We show that as a result of this mechanism the levels with \Delta Mj>2
give negligible contributions to the Zeemam relaxation cross section. We also
compare our results to the experimental cross sections obtained from the buffer
gas cooling and magnetic trapping of this molecule and investigate the
dependence of the Zeeman relaxation cross section on the accuracy of the three
body interaction at ultralow energies.
