研究目的
Investigating the effects of two methyl internal rotations and quadrupole coupling in 4,5-dimethylthiazole by microwave spectroscopy.
研究成果
The microwave spectrum of 45DMTA with five torsional species and 14N quadrupole hyperfine splittings were recorded under molecular jet conditions and successfully assigned assisted by quantum chemistry. Highly accurate molecular parameters were determined using the programs XIAM und BELGI-CS-2Tops-hyperfine. The torsional barriers of both methyl groups in 45DMTA are low, which is most probably due to potential coupling between the two methyl groups arising from motions with an anti-geared character.
研究不足
The XIAM fit has a root-mean-square deviation of 399.8 kHz, which is 100 times the estimated measurement accuracy of 4.0 kHz. This can be explained by the relatively low hindering potentials of both methyl groups and the rather significant coupling between the two tops.
1：Experimental Design and Method Selection:
The study used a COBRA-type pulsed molecular jet Fourier transform microwave spectrometer covering the frequency range from
2：0 to 5 GHz. The sample was placed on a piece of a pipe cleaner as carrier material, which was inserted in a stainless steel tube close to the nozzle. Helium at a pressure of approximately 200 kPa flowed over the sample and the resulting 45DMTA-helium mixture was expanded into the Fabry-Pérot cavity. Sample Selection and Data Sources:
The sample of 45DMTA was purchased from TCI Deutschland GmbH, Eschborn, Germany, with a stated purity of over 97% and used without further purification.
3：List of Experimental Equipment and Materials:
COBRA-type pulsed molecular jet Fourier transform microwave spectrometer, helium gas, 4,5-dimethylthiazole sample.
4：Experimental Procedures and Operational Workflow:
The time domain signal was Fourier transformed to obtain the spectrum. Each rotational transition is split into two components due to the Doppler effect. The rest frequency is calculated as the arithmetic mean of the frequencies of the Doppler components.
5：Data Analysis Methods:
The molecular parameters were determined using the programs XIAM and BELGI-Cs-2Tops-hyperfine, treating two methyl internal rotations and a weakly coupling quadrupole nucleus.
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