Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China.
J Chem Phys. 2013 Dec 28;139(24):244303. doi: 10.1063/1.4851475.
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.
我们报告了气态 UF(x)(-)（x = 2-4）阴离子的实验观察结果，这些阴离子是通过光电光谱法和相对论量子化学进行研究的。我们获得了所有三种物质的振动分辨光电电子能谱，并且测量了 UF(x)（x = 2-4）的电子亲和能分别为 1.16(3)、1.09(3)和 1.58(3) eV。在 U(5f(3)7s(2))F2(-)的光电电子光谱中观察到了显著的多电子跃迁，这是由于两个 7s 电子的强电子相关效应。在所有 UF(x)（x = 2-4）中性体的基态中，我们都解析了 U-F 对称伸缩振动模式。我们进行了理论计算，以定性理解光电电子光谱。我们从理论上考虑了整个 UF(x)(-)和 UF(x)（x = 1-6）系列，以研究 U-F 键合和电子亲和能随氟配位数的变化趋势。从 UF2(-)到 UF4(-)，U-F 键长的增加和键序的降低表明，随着 U 的氧化态从 I 增加到 III，U-F 键合变得越来越弱。
