Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
J Chem Phys. 2012 Jan 7;136(1):014304. doi: 10.1063/1.3673570.
The normal-to-local transition for the bending modes of acetylene is considered a prelude to its isomerization to vinylidene. Here, such a transition in fully deuterated acetylene is investigated using a full-dimensional quantum model. It is found that the local benders emerge at much lower energies and bending quantum numbers than in the hydrogen isotopomer HCCH. This is accompanied by a transition to a second kind of bending mode called counter-rotator, again at lower energies and quantum numbers than in HCCH. These transitions are also investigated using bifurcation analysis of two empirical spectroscopic fitting Hamiltonians for pure bending modes, which helps to understand the origin of the transitions semiclassically as branchings or bifurcations out of the trans- and cis-normal bend modes when the latter become dynamically unstable. The results of the quantum model and the empirical bifurcation analysis are in very good agreement.
乙炔的弯曲模式从常态到局域的转变被认为是其向乙烯叉异构化的前奏。在这里，使用全维量子模型研究了完全氘代乙炔中的这种转变。研究发现，与氢同位素 HCCH 相比，局域弯曲模式出现在能量更低和弯曲量子数更小的情况下。这伴随着向第二种弯曲模式的转变，称为反旋转器，其能量和量子数也比在 HCCH 中低。使用两个纯弯曲模式经验谱拟合哈密顿量的分岔分析也研究了这些转变，这有助于从半经典的角度理解转变的起源，即当反式和顺式常态弯曲模式变得动态不稳定时，它们从分支或分岔出来。量子模型和经验分岔分析的结果非常吻合。
