Accession Number : AD0666791

Title :   RARE EARTH INFRARED LIFETIMES AND EXCITON MIGRATION RATES IN TRICHLORIDE CRYSTALS

Descriptive Note : Technical rept.

Corporate Author : JOHNS HOPKINS UNIV BALTIMORE MD DEPT OF PHYSICS

Personal Author(s) : Gandrud, William B ; Moos, H W

PDF Url : AD0666791

Report Date : Jan 1968

Pagination or Media Count : 142

Abstract : Lifetimes of trivalent rare earth ion levels below 14,000/cm were measured in the LaCl3, GdCl3, and YCl3 hosts, using the Infrared Quantum Counter and infrared fluorescence techniques. Because of their low radiative and multiphonon relaxation rates, these levels are well suited to concentration- quenching studies. Temperature dependences provide evidence that the ion pair decays of four levels in Pr(3+) and Nd(3+) occur resonantly (i.e., without phonon assistance) between excited Stark components. This enables the measured decay rates for these four levels to be used in estimating the rate for a single resonant transfer of all of the ion's energy to a neighboring ion. This latter process is the basic step of the excitation migration process. From the lifetimes of a number of levels which are quenched by migration of the excitation to 'sinks,' an estimate of 400,000 is obtained for the number of transfers that occur before a sink is reached. Levels quenched by migration to sinks are found to decay exponentially, with a lifetime which increases with increasing crystal purity. The roles of the various relaxation processes in determining the performance of the Infrared Quantum Counter as an infrared detector are discussed.

Descriptors :   *EXCITONS, *INFRARED SPECTROSCOPY, *RARE EARTH ELEMENTS, ATOMIC ENERGY LEVELS, CHLORIDES, CRYSTAL DEFECTS, GADOLINIUM COMPOUNDS, INFRARED DETECTORS, IONS, LANTHANUM COMPOUNDS, QUENCHING(INHIBITION), RARE EARTH COMPOUNDS, RELAXATION TIME, STARK EFFECT, YTTRIUM COMPOUNDS

Subject Categories : Lasers and Masers
      Atomic and Molecular Physics and Spectroscopy
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE