Kemp David J, Fryer Elizabeth F, Davies Alexander R, Wright Timothy G
School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom.
J Chem Phys. 2019 Aug 28;151(8):084311. doi: 10.1063/1.5116520.
Zero-kinetic-energy (ZEKE) spectra are presented for m-fluorotoluene, employing different low-lying (<350 cm) intermediate torsional and vibration-torsional ("vibtor") levels of the S state. The adiabatic ionization energy (AIE) is found to be 71 997 ± 5 cm (8.9265 ± 0.0006 eV). It is found that the activity in the ZEKE spectra varies greatly for different levels and is consistent with the assignments of the S levels deduced in the recent fluorescence study of Stewart et al. [J. Chem. Phys. 150, 174303 (2019)]. For cation torsional levels, the most intense band corresponds to changes in the torsional quantum number, in line with the known change in the phase of the torsional potential upon ionization. This leads to the observation of an unprecedented number of torsions and vibtor levels, with the pronounced vibtor activity involving out-of-plane vibrations. Interactions between levels involving torsions are discussed, with evidence presented, for the first time it is believed, for modification of a torsional potential induced by a vibration. Also, we discuss the possibility of distortion of the methyl group leading to a change from G molecular symmetry to C point group symmetry.
给出了间氟甲苯的零动能（ZEKE）光谱，采用了S态不同的低激发（<350 cm）中间扭转和振动 - 扭转（“振动扭转”）能级。发现绝热电离能（AIE）为71997±5 cm（8.9265±0.0006 eV）。结果发现，ZEKE光谱中的活性因不同能级而有很大差异，并且与Stewart等人最近的荧光研究[《化学物理杂志》150, 174303 (2019)]中推导的S能级归属一致。对于阳离子扭转能级，最强的谱带对应于扭转量子数的变化，这与电离时扭转势相的已知变化一致。这导致观察到前所未有的扭转和振动扭转能级数量，其中明显的振动扭转活性涉及面外振动。讨论了涉及扭转的能级之间的相互作用，首次有证据表明（据信）振动会引起扭转势的改变。此外，我们讨论了甲基扭曲导致从G分子对称性变为C点群对称性的可能性。
