Perry David S
Department of Chemistry, The University of Akron, Akron, Ohio 44315-3601, USA.
J Phys Chem A. 2008 Jan 17;112(2):215-23. doi: 10.1021/jp077269q. Epub 2007 Dec 23.
Through a fit to methanol CH overtone data, a previously developed 4-dimensional torsion-vibration Hamiltonian is extended to high CH stretch excitation as well as to high torsional excitation. The strength of the torsion-vibration coupling is found to increase with CH stretch excitation. Systematic patterns of near degeneracy (3-, 4-, and 6-fold) are found in different regions of quantum number space. In the region of the CH fundamentals, an approximate a diabatic separation of the torsion (slow degree of freedom) from the CH stretches (fast degrees of freedom) accounts for the pattern of the energy levels and for the signs of the torsional tunneling splittings. For the higher CH overtones (v(CH) > or = 4), a diabatic representation accounts for the torsional structure obtained from the fully coupled calculation and for certain trends found in the pattern of the energy levels.
通过对甲醇CH泛音数据的拟合，一个先前开发的四维扭转 - 振动哈密顿量被扩展到高CH伸缩激发以及高扭转激发。发现扭转 - 振动耦合强度随CH伸缩激发而增加。在量子数空间的不同区域发现了近简并（3重、4重和6重）的系统模式。在CH基频区域，扭转（慢自由度）与CH伸缩（快自由度）的近似非绝热分离解释了能级模式和扭转隧穿分裂的符号。对于较高的CH泛音（v(CH)≥4），非绝热表示解释了从完全耦合计算得到的扭转结构以及在能级模式中发现的某些趋势。
