The annealing effects of sodium chloride single crystals doped with Rh
3+ are studied by optical absorption spectroscopy. The technique of an
nealing is an alternative to the most common irradiation technique whi
ch has been described earlier by other workers on Rh3+ in different ma
trices. This is the first report of an optical absorption spectrum of
a Rh2+ site. The specific d-d transitions are well defined in the spec
trum.