Vibrational spectrum and force field of uranium hexafluoride

Abstract

A total of 44 bands in the infrared and Raman spectra of 238UF6 vapor has been measured using long-path absorption cells and multiple-reflection Raman cells. The types of contours exhibited by these bands, and analogous contours in the spectrum of SF 6 , are discussed. Overtone and combination bands with resolved Q branches are used to estimate the anharmonicity corrections for the stretching fundamentals. The infrared contours of 1'3 (at 228 K) and 1'4 (at 256 K) have yielded estimates for the Coriolis constants S3 and S4 that satisfy the sum rule. The 235 UF 6 -238 UF 6 frequency shifts in these fundamentals have also been measured. All of these data, plus vibrational amplitudes from the electron diffraction study of Seip, have been combined to determine the general quadratic harmonic force field of UF 6 . Only three valence force constants are appreciably different from zero: f, = 3.85 ± 0.05, f~ ~ fa -fa'a =0.12 ± 0.0 1, and f" (cis interaction) = 0.30 ± 0.02, all in mdyn/ A. The large differences between this force field and that previously determined for WF6 are attributed to the effects of f -orbital contributions in UF 6 •

Density functional investigations of the properties and thermochemistry of UFn and UCln (n=1,…,6)

“…The main stretch band 3 (t 1u ) was predicted at 631 cm Ϫ1 with PBE0 and 613 cm Ϫ1 with B3LYP, in good agreement with the experimental value 626 cm Ϫ1 . 32 The main bend band 4 (t 1u ) was predicted to be at 186 cm Ϫ1 with both functionals in exact agreement with the experimental measurement. 32 The infrared intensities were also found in reasonable agreement with experimental values.…”

“…32 The main bend band 4 (t 1u ) was predicted to be at 186 cm Ϫ1 with both functionals in exact agreement with the experimental measurement. 32 The infrared intensities were also found in reasonable agreement with experimental values. The IR intensity of the main stretch mode, 3 was predicted at 685 km/mole by B3LYP and 735 km/mole by PBE0, in close agreement with the experimental value 750 km/mole.…”

Density functional investigations of the properties and thermochemistry of UF6 and UF5 using valence-electron and all-electron approaches

“…[32][33][34][35][36] Fairly good agreement exists among all the experimental measurements, with variations of less than 2% in the positions of the peaks. [32][33][34][35][36] Fairly good agreement exists among all the experimental measurements, with variations of less than 2% in the positions of the peaks.…”

Photoelectron spectroscopy and theoretical studies of UF5− and UF6−

“…8 All six fundamental modes of vibration for the highly symmetric O h UF 6 are known from Raman and infrared spectroscopy. [9][10][11][12][13][14][15][16] The electronic structure of UF 6 has also been well studied with absorption spectroscopy, [17][18][19] electron impact spectroscopy, 20,21 and photoelectron spectroscopy (PES). 22,23 To understand these available experimental data, computational actinide chemistry has experienced a steady growth in developing better relativistic quantum chemistry methods.…”