A spectral change of the self-trapped exciton luminescence (4.3 and 3.
7 eV bands) in CsI has been observed at 4.2 and 77 K under hydrostatic
pressure up to 1 GPa. The result is discussed in connection with the
pressure shifts of the energies of the (GAMMA8-, GAMMA6+) and (GAMMA8-
, GAMMA8+) excitons with the s-like and d-like electron states, respec
tively.