Analysis of the Fourier transform and diode laser spectra of the ν3 fundamental of PuF6

Abstract A detailed analysis of the ν 3 band of PuF 6 is presented. The P , Q , and R branches of the fundamental transition and of several hot bands have been observed for a cooled gas sample of PuF 6 at very low pressure in a long path length cell. Both a Fourier transform spectrometer (resolution 6 × 10 −3 cm −1 ) and a diode laser (resolution 4 × 10 −4 cm −1 ) have been used. Wavenumbers of the rotational transitions, measured on the diode spectra, have led to accurate values for the band origin and the rotational line spacing constant. Octahedral fine-structure manifolds in the P and R branches, for low to moderate values of J , have yielded a value of the splitting parameter. However, in the high- J manifolds and throughout the entire Q branch, the fine structure deviates substantially from theory. These discrepancies are apparently the result of accidental resonances with rotational levels of one or two neighboring vibrational states.