Abstract
The energy absorbed from a laser pulse by the volatile uranyl complex UO/sub 2/(HFA)/sub 2/TBPO (HFA = 1,1,1,5,5,5-hexafluoropentane-2,4-dionato ion; TBPO = tributylphosphine oxide), irradiated on the nu/sub 3/ asymmetric stretching frequency of the uranyl group, has been determined as a function of laser-pulse fluence and frequency. It was found that this large molecule (M/sub r/ = 902) can absorb in excess of 50 photons without undergoing any measurable decomposition and that the photon absorption is accompanied by a significant shift of the nu/sub 3/ absorption band. In a complementary study, the laser photochemistry of mixtures of U/sup 16/O/sup 16/O(HFA)/sub 2/TMP and U/sup 16/O/sup 18/O(HFA)/sub 2/TMP (TMP = trimethyl phosphate) was examined at laser fluences sufficiently high (0.4 to 1.1 J cm/sup -2/) to lead to the decomposition of the irradiated molecule. The nu/sub 3/ frequencies of the above species are separated by 17 cm/sup -1/, and isotope separation factors as high as 50 were obtained for the two molecules under certain experimental conditions using parallel beam geometries. Examination of the effects of the 16/18 to 16/16 ratio in the irradiated sample and of the effects of laser fluence and sample pressure suggests that the laser photochemistry of this system ismore » dominated by collision-induced energy-transfer phenomena occurring after the laser pulse. 10 figures.« less
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