Upconverted hot luminescence of Cr4+ ions in Mg2GeO4

Nonequilibrium excited vibronic states of Cr4+ ions in Mg2GeO4 were studied with the upconverted hot-luminescence technique. From the discrete spectral peaks observed, information on the nonradiative relaxation of the Cr4+ ions was obtained. The phonon modes involved in the nonradiative relaxation were measured to be omega(1) = 451 +/- 20 cm(-1), omega(2) = 342 +/- 20 cm(-1), and omega(3) = 252 +/- 20 cm(-1). The experiment also shows the presence of an electronic bottleneck centered at similar to 2.1 eV. These findings are compared with results previously obtained in Cr4+-doped Mg2SiO4 and provide information on the nonradiative relaxation of the same ion in different host crystals. (C) 1996 Optical Society of America.