Group-Theoretical Treatment of Tunneling Splittings in the Methanol Dimer
Group-Theoretical Treatment of Tunneling Splittings in the Methanol Dimer
复制标题
甲醇二聚体中隧道分裂的群论处理
DOI：
10.1006/jmsp.1994.1010
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发表时间：
1994
影响因子：
1.4
通讯作者：
J. T. Hougen
中科院分区：
文献类型：
--
作者：
N. Ohashi;J. T. Hougen
从群论的观点、改进的内轴方法、可能的隧穿路径的近似描述和K = 0能级可以被自己处理的假设，预测了氢键甲醇二聚体的K = 0转动能级的隧穿分裂模式、选择规则和有效B值。结果表明，25种不同的隧穿运动是可能的，当两个甲醇单体是相同的，产生16个隧穿旋转水平K = 0：4个非简并A级，8个双简并E级，和4个四重简并G级。最近观察到的甲醇二聚体K = 0的a型微波光谱的总功能可以解释使用只有两个这些隧道运动，即内部旋转的两个不等价的甲基基团的二聚体。观测到的分裂的更精细的细节可能来自于剩下的23个隧穿运动中的一些。Tunnel分裂模式也预测的情况下，在二聚体中的两个甲醇是同位素不同的，但两个甲基顶部的C3 v对称性被保存。
Abstract Tunneling splitting patterns, selection rules, and effective B values for K = 0 rotational levels of the hydrogen-bonded methanol dimer are predicted from group-theoretical considerations, a modified internal axis method, approximate descriptions of possible tunneling paths, and the assumption that K = 0 levels can be treated by themselves. It is shown that 25 different tunneling motions are possible when the two methanol monomers are identical, giving rise to 16 tunneling-rotational levels for K = 0: four nondegenerate A levels, eight doubly degenerate E levels, and four fourfold degenerate G levels. The gross features of a recently observed methanol dimer K = 0 a -type microwave spectrum can be explained using only two of these tunneling motions, namely the internal rotation of each of the two inequivalent methyl groups in the dimer. Finer details of the observed splittings presumably arise from some of the remaining 23 tunneling motions. Tunneling splitting patterns are also predicted for cases in which the two methanols in the dimer are isotopically different, but the C 3 v symmetry of both methyl tops is preserved.