Upconverted luminescence from nonequilibrium vibronic states of Cr ions in forsterite

Influence of low-symmetry distortions on the luminescence of Cr4+-doped forsterite

By using pressure to vary the extent of nontetrahedral distortions of the Cr4+ site in Mg2SiO4, we reveal the important influence of the 3T1 state on the emission properties of the 3T2 state. We find that 3T1-3T2 mixing has a pronounced effect on the line shape and radiative decay rate of emission from the 3T2 state and that the extent of mixing depends critically on the magnitude of nontetrahedral distortions. The results provide an explanation for the wide variation of Cr4+ emission properties in different host lattices at ambient pressure and indicate that the tailoring of asymmetric distortions of luminescent centers represents an effective new strategy for tuning the linewidth of spectral transitions.

Upconverted hot-luminescence spectroscopy investigation of nonradiative relaxation in forsterite

Upper-state nonradiative relaxation in the 3.2-1.9-eV energy region of the excited-state manifold of Cr(4+)-doped forsterite is investigated. Measurements of the upconverted hot-luminescence spectra reveal two electronic bottlenecks and several phonon modes involved in the initial steps of the vibrational relaxation at different portions of the excited-state manifold.