Accession Number : ADA210653


Title :   Radiationless Transitions and Excited-State Absorption of Low-Field Chromium Complexes in Solids


Descriptive Note : Final technical rept. 1 Jan 1986-31 May 1989


Corporate Author : CONNECTICUT UNIV STORRS DEPT OF PHYSICS


Personal Author(s) : Bartram, Ralph H


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a210653.pdf


Report Date : 20 Jul 1989


Pagination or Media Count : 36


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.


Descriptors :   *PHOTOLUMINESCENCE , *TUNABLE LASERS , FREQUENCY , MEASUREMENT , RADIATION , SCATTERING , VIBRATION , TRANSITION METALS , PREDICTIONS , MODELS , HIGH TEMPERATURE , EXCITATION , RAMAN SPECTROSCOPY , THEORY , HIGH PRESSURE , CRYSTALS , QUENCHING , ASYMMETRY , PRESSURE , QUADRATIC EQUATIONS , TRANSITIONS , TWO PHOTON ABSORPTION , DOPING , CHROMIUM , ABSORPTION , ABSORPTION SPECTRA , LIFE SPAN(BIOLOGY) , ENERGY LEVELS , FIELD CONDITIONS , COMPRESSIVE PROPERTIES , LASER MATERIALS , THERMAL PROPERTIES , COUPLING(INTERACTION)


Subject Categories : Lasers and Masers
      Metallurgy and Metallography
      Crystallography
      Optics


Distribution Statement : APPROVED FOR PUBLIC RELEASE