Department of Physics, Tokyo Institute of Technology , Ohokayama, Meguro-ku, Tokyo 152-8551, Japan.
J Phys Chem A. 2013 Oct 3;117(39):10041-6. doi: 10.1021/jp400632g. Epub 2013 May 29.
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.
S2Cl2 是观察正-仲转变的候选物质。为了估计超精细分辨旋转态中的正-仲混合，使用两种不同的实验装置通过毫米波（mm-wave）光谱测量了纯旋转跃迁。使用超音速射流测量了约 20 K 的项值附近的跃迁，而使用干冰冷却的气体池测量了约 200 K 的跃迁。对天然丰度的 S2(35)Cl2 和 S2(35)Cl(37)Cl 同位素物种以及包括四阶和六阶离心畸变常数在内的旋转分子参数分配了数百个峰。在一些 Q 支跃迁中部分分辨出了超精细结构，这些结构与在厘米波区域通过 FTMW 光谱确定的超精细常数很好地吻合。利用我们在这项研究中确定的新旋转常数和之前的超精细常数，将有可能获得更可靠的正-仲混合比，并缩小在 mm 波区域观察正-仲转变的可能候选跃迁。
