PHOTOPYROELECTRIC-QUANTUM-YIELD SPECTROSCOPY AND QUANTUM-MECHANICAL PHOTOEXCITATION-DECAY KINETICS OF THE TI3+ ION IN AL2O3

Quadrature photopyroelectric spectra of the optical-to-thermal (nonradiative) energy conversion efficiency of Ti3+:Al2O3 crystals were found to yield good agreement between the experimental quantum-yield spectrum of this optical material and detailed quantum-mechanical calculations of the nonradiative and radiative deexcitation kinetics of the Ti3+ ion in the Al2O3 host matrix. Both inter- and intraconfigurational decay mechanisms of the excited-state manifold were considered including fast nonradiative relaxations. The experimental quantum-yield spectra were found to be dominated by intraconfigurational nonradiative relaxation below the excited- and ground-electronic-state manifold crossover energy, E(nr); and by internal conversion processes in the highly vibronically excited Ti3+ ion above E(nr). A one-parameter fit of the quantum-yield model to the data gave the intraconfigurational relaxation time constant tau(intra) for the Ti3+.Al2O3 System. The present combined experimental and theoretical approach can be more generally applicable to other optoelectronic systems exhibiting strong electron-lattice coupling.