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Published on: October 9, 2020
Magnetic hyperfine coupling of a methyl group undergoing internal rotation: a case study of methyl formate
M Tudorie1, L H Coudert, T R Huet
1Laboratoire de Physique des Lasers, Atomes et Molécules, UMR 8523 CNRS-Université Lille 1, Villeneuve d'Ascq, France.
Abstract:
The hyperfine structure of methyl formate was recorded in the 2-20 GHz range. A molecular beam coupled to a Fourier transform microwave spectrometer having an instrumental resolution of 0.46 kHz and limited by a Doppler width of a few kHz was used. A-type lines were found split by the magnetic hyperfine coupling while no splittings were observed for E-type lines. Symmetry considerations were used to account for the internal rotation of the methyl top and to derive effective hyperfine coupling Hamiltonians. Neglecting the spin-rotation magnetic coupling, the vanishing splittings of the E-type lines could be understood and analyses of the hyperfine patterns of the A-type lines were performed. The results are consistent with a hyperfine structure dominated by the magnetic spin-spin coupling due to the three hydrogen atoms of the methyl group.
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