Abstract
Time-resolved photoluminescence spectra of red HgI 2 crystals under two-photon excitation have been investigated at 10 v; K, and the results are compared with those under one-photon excitation. The bound-exciton luminescence under one-photon excitation decays with components of lifetimes of 74 and 240 v; ps. Under two-photon excitation, on the other hand, the luminescence shows a single exponential decay with a lifetime almost the same as the slow components under one-photon excitation. The present results indicate that, near the surface of the crystal, the presence of an extra non-radiative decay process would shorten the lifetime of bound excitons.