Schulenburg A M, Merkt F
Laboratorium fur Physikalische Chemie, ETH Zurich, CH-8092 Zurich, Switzerland.
J Chem Phys. 2009 Jan 21;130(3):034308. doi: 10.1063/1.3056385.
The pulsed-field-ionization zero-kinetic-energy photoelectron spectra of allene (C(3)H(4)) and perdeuterated allene have been recorded from the first adiabatic ionization energy up to 2200 cm(-1) of internal energy in the cations at a resolution sufficient to observe the full rotational structure. The intensity distributions in the spectra are dominated by vibrational progressions in the torsional mode, which were analyzed in the realm of a two-dimensional model of the Emultiply sign in circle(b(1) plus sign in circleb(2)) Jahn-Teller effect in the allene cation [C. Woywod and W. Domcke, Chem. Phys. 162, 349 (1992)]. Whereas the rotational structure of the transitions to the lowest torsional levels (0(0) and 4(1)) are regular and can be qualitatively analyzed in terms of a simple orbital ionization model, the rotational structure of the spectra of the 4(2) and 4(3) levels are strongly perturbed. The photoelectron spectrum of C(3)H(4) also reveals several weak vibrational bands in the immediate vicinity of these levels that are indicative of (ro)vibronic perturbations. A slight broadening of the transitions to the 4(1) levels compared to that of the vibronic ground state and the increase of the number of sharp features in the rotational structure of the spectrum of the 4(2) level point at the importance of large-amplitude motions not considered in previous treatments of the Jahn-Teller effect in the allene cation.
已记录了丙二烯（C₃H₄）和全氘代丙二烯的脉冲场电离零动能光电子能谱，范围从第一绝热电离能到阳离子内部能量达2200 cm⁻¹，分辨率足以观察到完整的转动结构。光谱中的强度分布主要由扭转模式的振动进展主导，这些振动进展在丙二烯阳离子[C. Woywod和W. Domcke，《化学物理》162, 349 (1992)]的E×（b₁ + b₂） Jahn - Teller效应二维模型范围内进行了分析。虽然向最低扭转能级（0(0)和4(1)）跃迁的转动结构是规则的，并且可以根据简单的轨道电离模型进行定性分析，但4(2)和4(3)能级光谱的转动结构受到强烈扰动。C₃H₄的光电子能谱在这些能级紧邻区域还揭示了几个弱振动带，这表明存在（转动 - ）振动电子扰动。与振动电子基态相比，向4(1)能级跃迁略有展宽，以及4(2)能级光谱转动结构中尖锐特征数量的增加，都表明在先前对丙二烯阳离子Jahn - Teller效应的处理中未考虑的大幅度运动的重要性。
