Spin-orbit relaxation in selenium

Atomic selenium was the first ground state atom for which spin-orbit relaxation was measured120. The deposition of the sub-levels is shown in Table 10. 

Excited atoms can be conveniently produced by flashing CSe2 in a large excess of inert gas which prevents any significant temperature rise. Relaxation processes can be identified, and their rates measured, by kinetic spectroscopy and plate density measurement. The atoms are produced by direct photolysis into the 43P, states 

The CSe formed is vibrationally excited. The overall spin change can be accounted for by postulating that the upper singlet is predissociated by a triplet state which correlates with the ground electronic-state fragments. 

In mixtures containing initially 0.05 torr CSe2 with 20-60 torr of argon, the rate of decay of Se(43P0) is proportional to the pressure of argon, which indicates that the only important relaxation step is 

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