Site-selective spectroscopy and crystal field analysis of Cm3+ diluted in CsCdBr3

The optical spectroscopy of the Cm-248(3+) ion diluted in the host crystal CsCdBr3 has been investigated by laser selective excitation, excited state absorption, and fluorescence spectroscopy. Three distinct Cm3+ sites were o bserved. The principal site was assigned to the symmetric dimer center and its electronic structure was studied in detail. Analysis of its spectra res ulted in the assignment of 58 energy levels up to 40 300 cm(-1). These meas ured levels were fitted to the parameters of an empirical Hamiltonian with an rms deviation of 27.3 cm(-1). The lifetimes of the six fluorescing level s have been measured at liquid-helium temperatures. Weak blue I-6(7/2) --> S-8(7/2) upconversion fluorescence was observed when pumping the blue-green S-8(7/2) --> P-6(5/2) absorption transitions of the principal site. It is explained by a phonon-assisted energy transfer mechanism. (C) 2000 Elsevier Science B.V. All rights reserved.