Photoacoustic spectroscopy studies of plutonium compounds .2. Fluorides, oxalates and hydroxides of Pu(IV) and Pu(VI)

The photoacoustic spectra of Pu(IV) and Pu(VI) as PuO22+ ions in fluoride, oxalate and hydroxide in polycrystalline samples are reported for the first time. The photoacoustic spectra of Pu(TV) in these compounds showed good agreement with that of electronic absorption spectra of Pu(IV) in 1 M HClO4 solution. The photoacoustic spectrum of Pu(IV) hydroxide is, however, conspicuous with the absence of the 540 nm band which was prominently seen in the normal absorption of Pu(IV). Further, from the similarity of the observed spectra with pu(4+) in ZrSiO4, ligand-field splitting of pu(4+) electronic states in these compounds could be identified. The photoacoustic spectra of PuO22+ fluoride, oxalate and hydroxide samples was correlated with the reported spectra of PuO22+ in 1 M HClO4. The intense absorption at 816 nm in PuO2(OH)(2) . H2O is attributed to an electronic transition with strong coupling to the Pu-O stretching mode. The evidence for a weak vibronic coupling of electronic states of PuO22+ is presented from plutonyl fluoride spectrum.