Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA.
J Chem Phys. 2012 Jul 21;137(3):034307. doi: 10.1063/1.4734312.
LaO(2) was produced in a pulsed laser-vaporization molecular beam source and studied by mass-analyzed threshold ionization (MATI) spectroscopy and ab initio electronic structure calculations. The calculations included density functional theory, second-order perturbation theory, coupled cluster theory, and complete active space self-consistent field methods. The adiabatic ionization energy of the molecule and vibrational frequencies of the molecule and its cation were measured accurately for the first time from the MATI spectrum. Numerous ionization processes of lanthanum dioxide, peroxide, and superoxide were considered; the (3)B(2) ← (4)B(2) electronic transition of the dioxide was assigned upon comparison with the observed spectrum. The ionization energy and O-La-O bending frequency of the (4)B(2) neutral state are 4.9760 (6) eV and 92 cm(-1), respectively. The La-O stretching and O-La-O bending frequencies of the (3)B(2) cationic state are 656 and 122 cm(-1), respectively. The (4)B(2) state is formed by two electron transfer from lanthanum to oxygen atoms, and the (3)B(2) state is produced by the further removal of a lanthanum 6s-based electron.
LaO(2) 是在脉冲激光蒸发分子束源中产生的，并通过质量分析阈值电离（MATI）光谱和从头算电子结构计算进行了研究。计算包括密度泛函理论、二级微扰理论、耦合簇理论和完全活性空间自洽场方法。首次通过 MATI 光谱准确测量了分子的绝热电离能以及分子及其阳离子的振动频率。考虑了二氧化镧、过氧化物和超氧化物的众多电离过程；通过与观察到的光谱进行比较，确定了二氧化物的（3）B(2)←(4)B(2)电子跃迁。（4）B(2)中性态的电离能和 O-La-O 弯曲频率分别为 4.9760(6) eV 和 92 cm(-1)。（3）B(2)阳离子态的 La-O 伸缩和 O-La-O 弯曲频率分别为 656 和 122 cm(-1)。（4）B(2)态是由镧向氧原子转移两个电子形成的，（3）B(2)态是通过进一步去除镧 6s 基电子形成的。
