Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zurich, Switzerland.
J Chem Phys. 2011 Sep 28;135(12):124310. doi: 10.1063/1.3638182.
The pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the X̃(+2)A(")←X̃(1)A' transition of CH(3)CHCH(2) (propene), CD(3)CDCD(2), and several partially deuterated isotopomers have been recorded in the region of their adiabatic ionization thresholds and up to 2000 cm(-1) of internal energy of the cations. The vibrational structure has been assigned on the basis of the frequency shifts resulting from deuteration of selected sites of the propene molecule. Two highly anharmonic progressions have been identified and assigned to the two torsional modes of the propene cation, the methyl and methylene torsions. The positions of the torsional levels could be approximately reproduced using one-dimensional models, allowing a semi-quantitative description of the potential energy surface along each torsional coordinate. The observation of forbidden vibrational bands and the analysis of their partially resolved rotational contours reveal the importance of the vibronic coupling between the X̃(+2)A(") and the Ã(+2)A(') states mediated by the methylene (ν(20)) and methyl (ν(21)) torsional modes.
X̃(+2)A(")←X̃(1)A' 跃迁的 CH(3)CHCH(2)（丙烯）、CD(3)CDCD(2) 和几个部分氘代同位素的脉冲场电离零动能光电子光谱已在其绝热电离阈值区域以及阳离子内部能达到 2000 cm(-1) 的范围内记录下来。振动结构是基于对丙烯分子选定部位氘化引起的频率位移来分配的。已经确定并分配了两个高度非谐进动，它们分别对应于丙烯阳离子的两个扭转模式，即甲基和亚甲基扭转。使用一维模型可以近似再现扭转能级的位置，从而对每个扭转坐标的势能表面进行半定量描述。观察到禁戒振动带，并分析其部分分辨的旋转轮廓，揭示了 X̃(+2)A(")和Ã(+2)A(')态之间通过亚甲基（ν(20))和甲基（ν(21))扭转模式介导的振子耦合的重要性。
