Dynamical processes on relaxed excited states in NH4Cl:Tl+ single crystals

Abstract

AbstractWe have investigated the temperature dependence of temporal behaviors of the AX and AT luminescence bands in NH4Cl:Tl+ single crystals under an ArF excimer laser excitation. The time‐resolved AX luminescence spectra reveal the existence of two luminescence bands which are attributed to the radiative transitions from the relaxed 3T1u and 3A1u states, respectively. The slow decay of the luminescence due to the transition from the 3A1u state in the AX band becomes fast with increasing temperature from 16 K to 27 K. Then, the AT band exhibits a temporal rise reflecting the non‐radiative transition from the AX to AT minima on the adiabatic potential energy surface for the 3A1u state. The temperature dependence of the slow decay time of the AX band is analyzed by using the WKB method considering the non‐radiative transitions from vibrational energy levels in the adiabatic potential well. As a results, the temperature dependence can be fitted by taking the TA phonon energy of the NH4Cl bulk crystal as the separation energy between the vibrational energy levels. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)