title: Millimeter-wave spectroscopy of S2Cl2: a candidate molecule for measuring ortho-para transition.
abstract: S2Cl2 is a candidate for the observation of ortho-para transition. To estimate the ortho-para mixing in a hyperfine-resolved rotational state, pure rotational transitions were measured by millimeter-wave (mm-wave) spectroscopy using two different experimental set-ups. The transitions from the term value around 20 K was measured with a supersonic jet and those around 200 K were measured with a dry ice cooled gas cell. Several hundred peaks were assigned for the naturally abundant S2(35)Cl2 and S2(35)Cl(37)Cl isotopic species and the rotational molecular parameters including the fourth-order and sixth-order centrifugal distortion constants were determined. The hyperfine structures were partly resolved in some Q-branch transitions, which were well described with the hyperfine constants determined by FTMW spectroscopy in the centimeter-wave region. With the new rotational constants determined in our study and the previous hyperfine constants, it will be possible to obtain a more reliable ortho-para mixing ratio and to narrow down the possible candidate transitions in the mm-wave region for the observation of ortho-para transition.
authors: Department of Physics, Tokyo Institute of Technology , Ohokayama, Meguro-ku, Tokyo 152-8551, Japan.
authors: Zeinab Tafti
authors: ZT
authors: Dehghani
authors: Shinji
authors: S
authors: Ota
authors: Asao
authors: A
authors: Mizoguchi
authors: Hideto
authors: H
authors: Kanamori