Isotope Effects on Ground and Excited States of Ethyl Cation, H + (C 2 H 4 )
Isotope Effects on Ground and Excited States of Ethyl Cation, H + (C 2 H 4 )
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同位素对乙基阳离子 H (C 2 H 4 ) 基态和激发态的影响
DOI：
10.1021/acs.jpca.2c07334
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
McCoy, Anne B.
中科院分区：
文献类型：
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作者：
Moonkaen, Pattarapon;Finney, Jacob M.;McCoy, Anne B.
用扩散蒙特卡罗(DMC)方法研究了乙基阳离子H+(C2H4)及其氢化类似物的结构和光谱。这些计算都表明，尽管桥联质子的振动幅度很大，但H+(C2H4)的基态波函数定域在超额质子处于桥联构型的最小能量组态附近。而只有H+(C2D4)中的亚乙基氢原子的氢化对桥质子运动的幅度影响不大。用固定结点DMC计算了H+(C2H4)中通过光谱观察到的跃迁所进入的激发态。乙烯CH伸缩振动中单量子激发态的计算频率与实测值符合得很好。我们还研究了桥质子的质子转移振动中的一量子激发态，得到了H+(C2H4)的频率为616 cm-1。这一频率在H+(C2D4)中增加到629 cm-1。在D+(C2H4)和D+(C2D4)中，氢化使这一频率分别降至491和495厘米-1。还讨论了部分氚对CH伸缩振动频率的影响，以及相应的几率振幅。最后，我们报道了本研究中所考虑的四种乙基阳离子同位素的振动平均转动常数。
The structure and spectra of ethyl cation, H+(C2H4), and its deuterated analogues are investigated using diffusion Monte Carlo (DMC). These calculations all show that the ground state wave function for H+(C2H4) is localized near the minimum energy configuration in which the excess proton is in a bridging configuration, although the amplitude of the vibrational motions of the bridging proton is large. Deuteration of the bridging proton reduces the amplitude of this motion, while deuteration of only the ethylenic hydrogen atoms in H+(C2D4) has little effect on the amplitude of the motion of the bridging proton. Excited states that are accessed by spectroscopically observed transitions in H+(C2H4) are calculated using fixed-node DMC. The calculated and measured frequencies for the states with one quantum of excitation in the ethylenic CH stretching vibrations show good agreement. We also explore the excited state with one quantum of excitation in the proton transfer vibration of the bridging proton and obtain a frequency of 616 cm–1for H+(C2H4). This frequency increases to 629 cm–1in H+(C2D4). Deuteration decreases this frequency to 491 and 495 cm–1in D+(C2H4) and D+(C2D4), respectively. The effects of partial deuteration on the frequencies of the CH stretching vibrations, and the corresponding probability amplitudes are also explored. Finally, we report the vibrationally averaged rotational constants for the four isotopologues of ethyl cation considered in this study.