Electronic Spectroscopy of UO2Cl2 Isolated in Solid Ar

Abstract

Laser-induced fluorescence spectra have been recorded for uranyl chloride isolated in a solid Ar matrix. Pulsed excitation was examined using a XeCl excimer laser (308 nm) and a dye laser operating in the 19 500−27 500 cm−1 range. Several absorption and emission band systems were observed. The emission spectra were characterized by a nearly harmonic vibrational progression with a frequency of 840 cm−1 starting at 20 323 cm−1. The electronic absorption spectra were dominated by five harmonic vibrational progressions with frequencies of approximately 710 cm−1. Comparisons with theoretical calculations indicate that all of the transitions observed were associated with the UO2+2 subunit. They involved the promotion of an electron from a bonding orbital to the metal-centered 5fδ and 5fϕ orbitals. Band origins and vibrational constants for five excited states were obtained. Fluorescence was observed from the lowest-energy excited state alone, regardless of the excitation wavelength. The decay curve was found to be biexponential, with characteristic decay lifetimes of 50 and 260 μs.