Marks Joshua H, Miliordos Evangelos, Duncan Michael A
Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA.
Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, USA.
J Chem Phys. 2021 Feb 14;154(6):064306. doi: 10.1063/5.0041069.
RG-Co(HO) cation complexes (RG = Ar, Ne, He) are generated in a supersonic expansion by pulsed laser vaporization. Complexes are mass-selected using a time-of-flight spectrometer and studied with infrared laser photodissociation spectroscopy, measuring the respective mass channels corresponding to the elimination of the rare gas "tag" atom. Spectral patterns and theory indicate that the structures of the ions with a single rare gas atom have this bound to the cobalt cation opposite the water moiety in a near-C arrangement. The O-H stretch vibrations of the complex are shifted compared to those of water because of the metal cation charge-transfer interaction; these frequencies also vary systematically with the rare gas atom attached. The efficiencies of photodissociation also vary with the rare gas atoms because of their widely different binding energies to the cobalt cation. The spectrum of the argon complex could only be measured when at least three argon atoms were attached. In the case of the helium complex, the low binding energy allows the spectra to be measured for the low-frequency H-O-H scissors bending mode and for the O-D stretches of the deuterated analog. The partially resolved rotational structure for the antisymmetric O-H and O-D stretches reveals the temperature of these complexes (6 K) and establishes the electronic ground state. The helium complex has the same B ground state as the tag-free complex studied previously by Metz and co-workers ["Dissociation energy and electronic and vibrational spectroscopy of Co(HO) and its isotopomers," J. Phys. Chem. A 117, 1254 (2013)], but the A rotational constant is contaminated by vibrational averaging from the bending motion of the helium.
通过脉冲激光蒸发在超声速膨胀中产生RG-Co(HO)阳离子络合物（RG = Ar、Ne、He）。使用飞行时间光谱仪对络合物进行质量选择，并通过红外激光光解离光谱进行研究，测量与稀有气体“标签”原子消除相对应的各个质量通道。光谱模式和理论表明，含有单个稀有气体原子的离子结构中，该稀有气体原子以近C排列方式与钴阳离子结合在与水部分相对的位置。由于金属阳离子电荷转移相互作用，络合物的O-H伸缩振动与水的相比发生了位移；这些频率也随所连接的稀有气体原子而系统地变化。由于稀有气体原子与钴阳离子的结合能差异很大，光解离效率也随稀有气体原子而变化。只有当至少连接三个氩原子时才能测量氩络合物的光谱。对于氦络合物，低结合能使得能够测量低频H-O-H剪刀弯曲模式以及氘代类似物的O-D伸缩的光谱。反对称O-H和O-D伸缩的部分分辨转动结构揭示了这些络合物的温度（6 K）并确定了电子基态。氦络合物与Metz及其同事先前研究的无标签络合物具有相同的B基态[《Co(HO)及其同位素异构体的离解能、电子和振动光谱》，《物理化学杂志A》1,17, 1254 (2013)]，但A转动常数受到氦弯曲运动振动平均的影响。
