title: Probing the electronic structures of low oxidation-state uranium fluoride molecules UF(x)- (x = 2-4).
abstract: We report the experimental observation of gaseous UF(x)(-) (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 UF(x) (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))F2(-), 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 UF(x) (x = 2-4) neutrals. Theoretical calculations are performed to qualitatively understand the photoelectron spectra. The entire UF(x)(-) and UF(x) (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.
authors.affiliation: Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Wei-Li
authors.initials: WL
authors.lastname: Li
authors.affiliation: Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China.
authors.forename: Han-Shi
authors.initials: HS
authors.lastname: Hu
authors.affiliation: Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Tian
authors.initials: T
authors.lastname: Jian
authors.affiliation: Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Gary V
authors.initials: GV
authors.lastname: Lopez
authors.affiliation: Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Su
authors.affiliation: Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Lai-Sheng
authors.initials: LS
authors.lastname: Wang