Femtosecond pump-probe measurements of non-radiative relaxation in LiAlO2:V3+

We report on time-resolved studies of non-radiative relaxation of V3+ ions in LiAlO2 by means of a two-beam, pump-probe saturation experiment performed with the 150 fs pulsed output of a Ti-sapphire laser. Exciting into the vibronically broadened 3A2 →3T1 transition at 800 nm, a 3T1 relaxation time of 199 ps has been measured at 4 K. This value decreases to 82 ps at room temperature, representing a reduction in the lifetime of a factor of 2.5 due to internal-conversion processes. The relative probabilities for non-radiative, phonon-assisted barrier hopping and quantum mechanical tunnelling through the potential barrier to the 3A2 ground state have been obtained using Mott's expression, yielding best-fit parameters of W0 = (5.2 ± 1) x 109 Hz and W1 = (7.5 ± 1) x 1010 Hz for a potential barrier of Enr = 530 ± 50 cm-1