Atomic selenium was produced in a non-Boltzmann electronic distribution amongst the 43P spin-orbit multiplets, by flash photolysis of CSe2 in an excess of inert gas. Deactivation rates of Se(43P0) were recorded by kinetic spectroscopy in Ar, N2O, CO2, N2, CO, H2 and O2. Except for O2 and H2, which induce abnormally fast relaxation, the results show an approximate correlation with V-T and V-V energy transfer.