Site-dependent decay rates and fluorescence line narrowing ofMo3+in phosphate glass

Nonexponential fluorescence decays with rates varying with emission wavelength by more than a factor of 25 are measured for the ${}_{}{}^2{}_{}{}^{}E\to {}_{}{}^4{}_{}{}^{}A_2^{}{}_{}{}^{}$ emission from ${\mathrm{Mo}}^{3+}$ in phosphate glass. Based upon estimated radiative decay rates and the strong temperature dependence of the observed decay rates, the decay occurs principally by multiphonon emission. The large variation in rates is attributed to site-dependent differences in the strength of the ion-phonon coupling. Time-resolved broadband-excited fluorescence spectra exhibit line narrowing and spectral shifts with time. Fluorescence spectra obtained using a tunable laser to excite the ${}_{}{}^4{}_{}{}^{}A_2^{}{}_{}{}^{}-{}_{}{}^2{}_{}{}^{}E$ transition exhibit a small amount of line narrowing and establish that the emission from ${\mathrm{Mo}}^{3+}$ in glass is predominantly vibronic in nature.