1. The effects of proton tunneling, 14N quadrupole coupling, and methyl internal rotations in the microwave spectrum of ethyl methyl amine
- Author
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Ha Vinh Lam Nguyen, Wolfgang Stahl, Kenneth J. Koziol, Rheinisch-Westfälische Technische Hochschule Aachen University (RWTH), Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA (UMR_7583)), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), ANR-18-CE29-0011,PARIS-FTMW,Un nouveau spectromètre microonde par transformée de Fourier et jet moléculaire combinant un résonateur et un chirp pulsé pour enregistrer rapidement des spectres à haute résolution et discriminer des énantiomères(2018), Rheinisch-Westfälische Technische Hochschule Aachen (RWTH), and Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Paris (UP)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)
- Subjects
Coupling constant ,Materials science ,010304 chemical physics ,Spectrometer ,Analytical chemistry ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,Spectral line ,0104 chemical sciences ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,chemistry.chemical_compound ,symbols.namesake ,Fourier transform ,chemistry ,0103 physical sciences ,Quadrupole ,symbols ,Physical and Theoretical Chemistry ,Microwave ,Quantum tunnelling ,Methyl group - Abstract
International audience; The spectra of N-ethyl methyl amine, CH3(NH)CH2CH3, were measured using a molecular jet Fourier transform microwave spectrometer in the frequency range of 2 GHz–26.5 GHz. Splittings due to proton inversion tunneling, Coriolis coupling, 14N quadrupole coupling, and methyl internal rotation were fully resolved. The experimentally deduced rotational constants are A = 25 934.717(21) MHz, B = 3919.8212(23) MHz, and C = 3669.530(21) MHz. The proton tunneling causes (+) ↔ (−) splittings of about 1980.9 MHz for all c-type transitions between the lowest symmetric and the higher anti-symmetric energy levels. The splittings of the (+) ← (+) and (−) ← (−) levels, mainly influenced by Coriolis coupling, were also observed and assigned for b-type transitions, yielding the coupling constants Fbc = 0.3409(71) MHz and Fac = 163.9(14) MHz. The 14N quadrupole coupling constants were determined to be χaa = 2.788 65(55) MHz and χbb − χcc = 4.630 45(91) MHz. Fine splittings arising from two inequivalent methyl rotors are in the order of 150 kHz, and the torsional barriers are determined to be 1084.62(41) cm−1 for the CH3NH methyl group and 1163.43(80) cm−1 for the CH2CH3 methyl group. The experimental results are in good agreement with those of quantum chemical calculations.
- Published
- 2020
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