About cookies on this site Our websites require some cookies to function properly (required). In addition, other cookies may be used with your consent to analyze site usage, improve the user experience and for advertising. For more information, please review your options. By visiting our website, you agree to our processing of information as described in IBM’sprivacy statement. To provide a smooth navigation, your cookie preferences will be shared across the IBM web domains listed here.
Paper
Anharmonic vibrational relaxation dynamics for a molecular impurity mode in alkali halide crystals
Abstract
High-resolution diode-laser spectroscopy and the nonequilibrium techniques of incoherent laser saturation and transient hole-burning spectroscopy have been used to measure the relaxation dynamics (specifically T1 and T2) of the 3 internal vibrational mode of ReO4- molecules as functions of temperature and host alkali halide lattice. Inhomogeneously broadened linewidths less than 0.02 cm-1 were observed in annealed crystals at low temperatures. To retrieve the homogeneous linewidths from the inhomogeneously broadened lines, hole-burning measurements of T2 were performed with the use of a CO2 laser as a saturating pump and either a Pb-salt diode laser or another CO2 laser as a tunable probe. Holes as narrow as 10 MHz (full width at half maximum) were observed in inhomogeneously broadened lines several cm-1 wide. Excited-state lifetimes T1 were measured by CO2-laser saturation measurements, which provide values for the saturation intensity Is and hence the product T1T2. Above 10 K the dominant dephasing (T2) mechanism is acousticphonon scattering, whereas below 10 K T2 achieves the fundamental upper limit of 2T1, signifying that dephasing is lifetime limited. The results of a systematic study of the alkali halide host lattice dependence of the excited-state decay rate at low temperatures show that the decay channel consists of multistep emission of lower-energy internal modes, localized phonon modes, and band phonons. © 1984 The American Physical Society.