LASER SPECTROSCOPY AND CRYSTAL-FIELD ANALYSIS OF CM3+ DILUTED IN CS2NAYCL6

Laser selective excitation, excited state absorption, two-photon absor ption, and fluorescence line narrowing techniques have been used to in vestigate the electronic energy level structure of the Cm3+ ion dilute d in the host crystal Cs2NaYCl6. In this crystal the Cm3+ ion replaces a Y3+ ion at an octahedral site (O-h symmetry). Analysis of these spe ctra resulted in the assignment of 52 energy levels, which were fitted to the parameters of an empirical Hamiltonian with a rms deviation of 57 cm(-1). Many of the Gamma(8) symmetry levels exhibited small split tings, which was indicative of a site symmetry lower than O-h. The ene rgies of the most prominent vibronic features have been measured and a ssigned to specific vibrational modes of the CmCl63- moiety or to latt ice modes. The lifetimes of four fluorescing levels have been obtained at room and liquid helium temperatures. These were analyzed to determ ine the processes which contribute to the relaxation of an excited Cm3 + ion in this host. Blue P-6(5/2)-->S-7/2 upconversion fluorescence wa s observed when pumping the orange S-8(7/2)-->D-6(7/2) absorption tran sitions and explained by a phonon-assisted energy transfer mechanism. (C) 1998 American Institute of Physics. [S0021-9606(98)02615-4].