Multiphonon relaxation in YVO4 single crystals

Multiphonon relaxation rates were measured for 13 different energy levels of various rare-earth ions in YVO4 single crystals at 77 K. Dependence of the multiphonon relaxation rate on the energy gap that separates each emitting multiplet from the one lying just below it was investigated over the range from 980 to 5200 cm(-1). A significant change in gap dependence was observed for energy gaps smaller than about 2500 cm(-1), in agreement with previous observations and with theoretical investigations. An extreme nonradiative transition rate of 1.1 x 10(11) s(-1) (tau = 9 ps), corresponding to a 980 cm(-1) energy gap, was deduced from homogeneous absorption linewidth measurements at 1.5 K.