Nguyen Ha Vinh Lam, Van Vinh, Stahl Wolfgang, Kleiner Isabelle
Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52074 Aachen, Germany.
Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), UMR 7583 (CNRS/Univ. Paris Est and Paris Diderot), Université de Paris Est, 61 avenue du Général de Gaulle, F-94010 Créteil cedex, France.
J Chem Phys. 2014 Jun 7;140(21):214303. doi: 10.1063/1.4878412.
The rotational spectra of ethyl methyl ketone, CH3CH2COCH3, were measured in the microwave region from 2 to 40 GHz using two molecular beam Fourier transform microwave spectrometers. Splittings due to internal rotations of both, the acetyl methyl group -COCH3 and the ethyl methyl group CH3CH2CO-, could be completely resolved. All measured transitions were fitted using two different codes, XIAM and BELGI-Cs-2Tops. Molecular parameters like the rotational constants and the centrifugal distortion constants were determined with very high accuracy. The barrier to internal rotation of the acetyl methyl group was fitted to 181.502(98) cm(-1), much lower than the value of 763.87(65) cm(-1) found for the ethyl methyl group. The splittings in the spectrum due to internal rotation of the acetyl methyl group are accordingly much larger, up to 1.2 GHz, whereas for the ethyl methyl group only splittings from a few hundreds of kHz up to 4 MHz were observed.
使用两台分子束傅里叶变换微波光谱仪，在2至40 GHz的微波区域测量了乙基甲基酮（CH3CH2COCH3）的转动光谱。乙酰基甲基-COCH3和乙基甲基CH3CH2CO-的内旋转引起的分裂都可以完全分辨出来。所有测量的跃迁都使用两种不同的程序XIAM和BELGI-Cs-2Tops进行拟合。像转动常数和离心畸变常数这样的分子参数被非常高精度地确定。乙酰基甲基的内旋转势垒拟合为181.502(98) cm(-1)，远低于乙基甲基的763.87(65) cm(-1)的值。因此，由于乙酰基甲基的内旋转，光谱中的分裂要大得多，高达1.2 GHz，而对于乙基甲基，只观察到几百千赫到4兆赫的分裂。
