Temperature dependence of the collisional relaxation processes for then=3triplet states of helium

Deactivation rates of the $n=3$ states of the triplet system of helium by collisions with ground-state helium atoms have been measured by time-resolved selective excitation spectroscopy with a short-pulse dye laser as a function of gas temperature from 300 to 600°K. Results are in generally good agreement with predictions of the multistate curve-crossing model for scattering recently proposed by J. S. Cohen; they bring complementary information on the relevant intermolecular potential and on coupling between states.