Coupled Large Amplitude Motions: A Case Study of the Dimethylbenzaldehyde Isomers

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• 作者：M. Tudorie ; I. Kleiner ; M. Jahn ; J.-U. Grabow ; M. Goubet ; O. Pirali
• 刊名：Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：December 19, 2013
• 年：2013
• 卷：117
• 期：50
• 页码：13636-13647
• 全文大小：461K
• 年卷期：v.117,no.50(December 19, 2013)
• ISSN：1520-5215

文摘

The microwave spectra of the 3,4- (syn and anti), 2,5- (syn), and 3,5-dimethylbenzaldehyde (DMBA) molecules have been recorded for the first time in the 2鈥?6.5 GHz frequency range, using the high resolution COBRA-FTMW spectrometer in Hannover. The experimental assignments and fits are supplemented by ab initio quantum chemical calculations of the conformational energy landscape and dipole moment components. The analysis of the spectra of the four observed isomers, including spectroscopic constants and large amplitude motion parameters, are presented in this paper. The DMBA isomers belong to a series of similar molecules obtained formally by adding one or more methyl group(s) at the aromatic ring. These molecules serve as prototype systems for the development of the theoretical model of asymmetric top molecules having C_s symmetry while containing in addition two nonequivalent methyl tops (C_3v), exhibiting different barrier heights and coupling terms. Thus, the DMBA isomers represent good species for testing the recently written two-top internal rotors BELGI program.