Two-Photon Absorption Spectroscopy of the Trivalent Cerium Ion in Calcium Fluoride

摘要

The two-photon transitions from the lowest 4f to the 5d states of the C/sub 4v/ center in Ce exp 3+ :CaF sub 2 from 31,900 to 50,500 cm exp -1 have been studied with a tunable dye laser as a function of laser wavelength, intensity, polarization and focusing geometry. A fluorescence detection technique was used to measure the two-photon absorption (TPA). The observed TPA spectra consist of two well resolved bands in the wavelength intervals 627 to 590 nm and 520 to 450 nm respectively, and two unresolved bands in the range 410 to 396 nm. At 8 degrees K the lowest energy band consists of a zero-phonon line accompanied by its vibrational sideband. The peak TPA cross section for the zero-phonon transition is of the order 5x10 exp -54 cm exp 4 sec, indicating significant crystal-field parity mixing for the participating states. The zero-phonon line shows a polarization anisotropy consistent with a Ce exp 3+ site of C/sub 4v/ symmetry. The phonon sideband has a frequency dependent polarization anisotropy. 76 references, 35 figures, 13 tables. (ERA citation 10:019311)