Koziol Kenneth J, Stahl Wolfgang, Nguyen Ha Vinh Lam
Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany.
Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR 7583, Université Paris-Est Créteil, Université de Paris, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil, France.
J Chem Phys. 2020 Nov 14;153(18):184308. doi: 10.1063/5.0025650.
The spectra of N-ethyl methyl amine, CH(NH)CHCH, 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, N 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 F = 0.3409(71) MHz and F = 163.9(14) MHz. The N quadrupole coupling constants were determined to be χ = 2.788 65(55) MHz and χ - χ = 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 for the CHNH methyl group and 1163.43(80) cm for the CHCH methyl group. The experimental results are in good agreement with those of quantum chemical calculations.
使用分子束傅里叶变换微波光谱仪在2 GHz - 26.5 GHz频率范围内测量了N - 乙基甲胺（CH₃NHCH₂CH₃）的光谱。质子反转隧穿、科里奥利耦合、N核四极耦合和甲基内旋转引起的分裂被完全分辨出来。实验推导的转动常数为A = 25934.717(21) MHz，B = 3919.8212(23) MHz，C = 3669.530(21) MHz。质子隧穿导致最低对称能级和较高反对称能级之间所有c型跃迁的(+) ↔ (-)分裂约为1980.9 MHz。还观察到并指定了主要受科里奥利耦合影响的(+) ← (+)和(-) ← (-)能级的分裂用于b型跃迁，得到耦合常数F = 0.3409(71) MHz和F = 163.9(14) MHz。N核四极耦合常数确定为χ = 2.78865(55) MHz和χ - χ = 4.63045(91) MHz。由两个不等价甲基转子引起的精细分裂约为150 kHz，并且确定CH₃NH甲基的扭转势垒为1084.62(41) cm⁻¹，CH₂CH₃甲基的扭转势垒为1163.43(80) cm⁻¹。实验结果与量子化学计算结果吻合良好。
