Abstract
In 1938, S. V. Raghava Rao reported that a crystal of HgXSCN (X=halogen) has photropic properties and in 1955, the author reported the mechanism of the phototropy is identical with that ofHgI2·2HgS.However, a behavior of S, I and C atoms in the crystals irradiated by sunlight was not known. Purpose of this paper is to clarify the behavior of these atoms by using radioactive tracer technique. The results obtained show that when electrons belonging to S2-or I-ions absorb photons and are excited to upper state, these electrons leave behind neutral S or I atoms, which diffuse thermally toward the crystal surface and escape into atmosphere.14C atoms do not escape. S atoms are more sensitive to light than I or C atoms.
