15min:

KAORI KOBAYASHI, YUSUKE SAKAI, SHOZO TSUNEKAWA, Department of Physics, University of Toyama, 3190 Gofuku, Toyama, 930-8555 Japan; TAIHEI MIYAMOTO, MASAHARU FUJITAKE AND NOBUKIMI OHASHI, Kanazawa University, Japan.

The trans -ethyl methyl ether molecule (CH₃CH₂OCH₃) has two inequivalent methyl group internal rotors which corresponds to the two vibrational motions, ₂₈ and ₂₉. Due to these internal rotations, a rotational transition could be split into maximum five components. The skeletal torsion ( ₃₀) is another low-lying state ( ₃₀) that interacts with the ₂₈ and ₂₉ modes. The microwave spectra of the trans -ethyl methyl ether molecule in the ₂₈ = 1 , ₂₉ = 1 , and ₃₀ = 1 , 2 and 3 have been extensively studied by using Hougen's tunneling matrix formalism. The microwave spectroscopy in the ground state was studied by several groups ^{, , ,} . The splitting due to the ₂₈ mode (C-CH₃ internal rotation) is small in the ground state and was not fully resolved in most of the previous studied rotational transitions.
In this paper, we report the results of the pulsed nozzle-jet Fourier transform microwave spectroscopy so as to measure the fully resolved spectra. The submillmeter wave spectroscopy was also carried out. Our analysis including the previously reported transitions would be useful for astronomical observations.