We report the experimental observation of gaseous UFx- (x = 2-4) anions, which are investigated using photoelectron spectroscopy and relativistic quantum chemistry. Vibrationally resolved photoelectron spectra are obtained for all three species and the electron affinities of UFx (x = 2-4) are measured to be 1.16(3), 1.09(3), and 1.58(3) eV, respectively. Significant multi-electron transitions are observed in the photoelectron spectra of U(5f(3)7s(2)) F-2(-), as a result of strong electron correlation effects of the two 7s electrons. The U-F symmetric stretching vibrational modes are resolved for the ground states of all UFx (x = 2-4) neutrals. Theoretical calculations are performed to qualitatively understand the photoelectron spectra. The entire UFx- and UFx (x = 1-6) series are considered theoretically to examine the trends of U-F bonding and the electron affinities as a function of fluorine coordination. The increased U-F bond lengths and decreased bond orders from UF2- to UF4- indicate that the U-F bonding becomes weaker as the oxidation state of U increases from I to III. (C) 2013 AIP Publishing LLC.
Revised: May 2, 2014 |
Published: December 28, 2013
Citation
Li W., H. Hu, T. Jian, G.V. Lopez, J. Su, J. Li, and L. Wang. 2013.Probing the electronic structures of low oxidation-state uranium fluoride molecules UFx- (x=2-4).Journal of Chemical Physics 139, no. 24:Article No. 244303.PNNL-SA-102026.doi:10.1063/1.4851475