Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
J Chem Phys. 2018 Nov 7;149(17):174301. doi: 10.1063/1.5053691.
The electronic spectra of Cr(NH), Cr(ND), and Cr(NH) have been measured from 14 200 to 17 400 cm using photodissociation spectroscopy. Transitions are predominantly observed from the A ground state, in which the Cr has a 3 electronic configuration, to the E (Π) state (3 4). There is extensive vibronic structure in the spectrum due to a long progression in the Cr-N stretch and transitions to all six spin-orbit levels in the upper state. The spin-orbit splitting in the excited state is observed to be A' = 39 cm. For the lowest spin-orbit level, the Cr-N stretching frequency in the excited state is 343 cm, with an anharmonicity of 4.2 cm. The E (Π) origin is predicted to lie at T = 14 697 cm. The first peak observed is due to v' = 1, so the observed photodissociation onset is thermodynamic rather than spectroscopic, giving D(Cr-NH) = 14 830 ± 100 cm (177.4 ± 1.2 kJ/mol) and D(Cr-ND) = 15 040 ± 30 cm (179.9 ± 0.4 kJ/mol). The E (Π) state of Cr(NH) is ∼2740 cm less strongly bound than the ground state, and the Cr-N bond length increases by 0.23 ± 0.03 Å upon electronic excitation. Calculations at the time-dependent density functional theory (M06) and equations of motion coupled cluster, with single and double excitations (EOM-CCSD) level fairly accurately predict the energy and vibrational frequency of the excited state. Multi-reference configuration interaction calculations show how the spin-orbit states of Cr(NH) evolve into those of Cr + NH.
Cr(NH)、Cr(ND)和 Cr(NH)的电子光谱已经通过光解光谱从 14200 到 17400cm-1 进行了测量。跃迁主要观察到从 A 基态（Cr 具有 3 电子构型）到 E（Π）态（3 4）。由于 Cr-N 拉伸的长进展以及跃迁到上态中的所有六个自旋轨道能级，光谱中存在广泛的振动态结构。在激发态中观察到自旋轨道分裂为 A'=39cm。对于最低的自旋轨道能级，激发态中的 Cr-N 伸缩频率为 343cm-1，非谐性为 4.2cm-1。预测 E（Π）的零点位于 T=14697cm-1。观察到的第一个峰归因于 v'=1，因此观察到的光解起始是热力学的而不是光谱的，给出 D(Cr-NH)=14830±100cm-1（177.4±1.2kJ/mol）和 D(Cr-ND)=15040±30cm-1（179.9±0.4kJ/mol）。Cr(NH)的 E（Π）态比基态弱结合约 2740cm-1，电子激发后 Cr-N 键长增加 0.23±0.03Å。在时变密度泛函理论（M06）和运动方程耦合簇，单重和双重激发（EOM-CCSD）水平的计算相当准确地预测了激发态的能量和振动频率。多参考组态相互作用计算显示了 Cr(NH)的自旋轨道态如何演变成 Cr+NH 的自旋轨道态。
