Radiationless Transitions and Excited-State Absorption of Low-Field Chromium Complexes in Solids
Abstract
The continuation of a coordinated experimental and theoretical investigation of photoluminescence quenching and excited-state absorption, major loss mechanisms in potential tunable laser materials, is reported. The materials investigated include chromium-doped crystals of cubic elpasolite structure: Cs2NaYCl6' K2NaScF6 and K2NaGaF6. Photoluminescence lifetimes, measured as functions of temperature and pressure in a diamond-anvil cell, revealed a pressure-induced shift of the onset of thermal quenching to higher temperatures. This observation is consistent with the predictions of a theoretical model, proposed earlier, in which radiationless de-activation of the chromium complex is mediated by quadratic coupling to an asymmetric vibrational mode. Ab-initio embedded-molecular-cluster calculations yielded predictions of the pressure dependence of local compressibility and localized vibration frequencies in good accord with experiment, thus demonstrating the predictive capability of theoretical modeling. Raman-scattering measurements in the diamond-anvil cell provided information about the pressure dependence of both localized and host- lattice vibration frequencies. Two-photon absorption experiments designed to characterize the vibronic structure of excited states are in progress, as a prelude to the investigation of excited-state absorption spectra. Keywords: Non- radiative transitions; Transition-metal complexes; Chromium; Tunable lasers; High pressure; Photoluminescence.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 20, 1989
- Accession Number
- ADA210653
Entities
People
- Ralph H. Bartram
Organizations
- University of Connecticut