Fourier Transform Microwave Spectra of the Nitrogen Molecule-Ethylene Sulfide and Nitrogen Molecule-Dimethyl Sulfide Complexes

Yoshiyuki Kawashima; Sakae Iwano; Eizi Hirota

doi:10.1021/acs.jpca.8b08647

Fourier Transform Microwave Spectra of the Nitrogen Molecule-Ethylene Sulfide and Nitrogen Molecule-Dimethyl Sulfide Complexes

J Phys Chem A. 2018 Dec 13;122(49):9454-9463. doi: 10.1021/acs.jpca.8b08647. Epub 2018 Nov 28.

Authors

Yoshiyuki Kawashima¹, Sakae Iwano¹, Eizi Hirota²

Affiliations

¹ Department of Applied Chemistry , Faculty of Engineering, Kanagawa Institute of Technology , Atsugi , Kanagawa 243-0292 , Japan.
² The Graduate University for Advanced Studies , Hayama , Kanagawa 240-0193 , Japan.

PMID: 30427672
DOI: 10.1021/acs.jpca.8b08647

Abstract

We recorded the rotational spectra of N₂-ethylene sulfide (ES) and N₂-dimethyl sulfide (DMS) including the ¹⁵N₂ and ¹⁵N¹⁴N isotopomers in the frequency range of 5-25 GHz by using a Fourier transform microwave spectrometer. The b-type transitions for the ortho and para states of ¹⁴N₂-ES and ¹⁵N₂-ES and c-type transitions of ¹⁴N₂-DMS and ¹⁵N₂-DMS were observed. The ¹⁵N¹⁴N-ES and ¹⁵N¹⁴N-DMS species were found to exist in two isomeric forms: inner (¹⁴N¹⁵N-ES and ¹⁴N¹⁵N-DMS) and outer (¹⁵N¹⁴N-ES and ¹⁵N¹⁴N-DMS). Neither the -ES nor -DMS complexes showed weak accompanying spectra, which had been observed for N₂-ethylene oxide (EO). This is because the potential barriers to internal rotation of ES and DMS are higher than that of EO. The spectra were analyzed by an A-reduced asymmetric-top rotational program with less than 4 kHz standard deviation, except for the ¹⁵N¹⁴N-DMS and ¹⁴N¹⁵N-DMS complexes. Rotational, centrifugal distortion, and nuclear electric quadrupole coupling constants were determined by the spectral analysis. The V₃ potential barrier to internal rotation of the two equivalent methyl groups of DMS in the ortho and para states of the ¹⁵N₂-DMS complex was determined to be about 740 cm^-1. We performed ab initio calculations in order to complement the information on the intracomplex motions obtained from the experimental spectra.