Boyer Mark A, Chiu Chloe S, McDonald David C, Wagner J Philipp, Colley Jason E, Orr Dylan S, Duncan Michael A, McCoy Anne B
Department of Chemistry, University of Washington, Seattle, Washington 98195, United States.
Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States.
J Phys Chem A. 2020 Jun 4;124(22):4427-4439. doi: 10.1021/acs.jpca.0c02299. Epub 2020 May 27.
The spectra for H and D are extended to cover the region between 4830 and 7300 cm. These spectra are obtained using mass-selected photodissociation spectroscopy. To understand the nature of the states that are accessed by the transitions in this and prior studies, we develop a four-dimensional model Hamiltonian. This Hamiltonian is expressed in terms of the two outer H stretches, the displacement of the shared proton from the center of mass of these two H groups, and the distance between the H groups. This choice is motivated by the large oscillator strength associated with the shared proton stretch and the fact that the spectral regions that have been probed correspond to zero, one, and two quanta of excitation in the H stretches. This model is analyzed using an adiabatic separation of the H stretches from the other two vibrations and includes the non-adiabatic couplings between H stretch states with the same total number of quanta of excitation in the H stretches. Based on the analysis of the energies and wave functions obtained from this model, we find that when there are one or more quanta of excitation in the H stretches the states come in pairs that reflect tunneling doublets. The states accessed by the transitions in the spectrum with the largest intensity are assigned to the members of the doublets with requisite symmetry that are localized on the lowest-energy adiabat for a given level of H excitation.
氢（H）和氘（D）的光谱范围扩展至4830至7300厘米之间。这些光谱通过质量选择光解离光谱法获得。为了理解在本研究及之前的研究中跃迁所涉及的态的性质，我们构建了一个四维模型哈密顿量。该哈密顿量用两个外部H伸缩振动、共享质子相对于这两个H基团质心的位移以及H基团之间的距离来表示。做出这种选择的动机是与共享质子伸缩相关的大振子强度，以及所探测的光谱区域对应于H伸缩振动中零、一和两个激发量子的事实。使用H伸缩振动与其他两个振动的绝热分离对该模型进行分析，并包括在H伸缩振动中具有相同总激发量子数的H伸缩态之间的非绝热耦合。基于对该模型所得能量和波函数的分析，我们发现当H伸缩振动中有一个或多个激发量子时，态会成对出现，反映出隧穿双重态。光谱中强度最大的跃迁所涉及的态被指定为具有必要对称性的双重态成员，这些成员在给定的H激发水平下位于最低能量绝热线上。
