Centre for Laser, Atomic and Molecular Physics, Department of Physics, University of New Brunswick, 100 Tucker Park Road, Saint John, New Brunswick E2L 4L5, Canada.
J Chem Phys. 2012 Sep 14;137(10):104313. doi: 10.1063/1.4745792.
In this work, terahertz and Fourier transform far-infrared (FTFIR) synchrotron spectra of methyl mercaptan, CH(3)SH, have been investigated in order to provide new laboratory information for enhanced observations of this species in interstellar molecular clouds and star-forming regions. Like its methanol cousin, methyl mercaptan has particularly rich spectra associated with its large-amplitude internal rotation that extend throughout the THz and FIR regions. We have recorded new spectra for CH(3)SH from 1.1-1.5 and 1.790-1.808 THz at the University of Cologne as well as high-resolution FTFIR synchrotron spectra from 50-550 cm(-1) at 0.001 cm(-1) resolution on the far-IR beam-line at the Canadian Light Source. Assignments are reported for rotational quantum numbers up to J ≈ 40 and K ≈ 15, and torsional states up to v(t) = 2 for the THz measurements and v(t) = 3 for the FTFIR observations. The THz and FTFIR measurements together with literature results have been combined in a global analysis of a dataset comprising a total of 1725 microwave and THz frequencies together with ~18000 FTFIR transitions, ranging up to v(t) = 2 and J(max) = 30 for MW∕THz and 40 for FTFIR. The global fit employs 78 torsion-rotation parameters and has achieved a weighted standard deviation of ~1.1. A prediction list (v(t) ≤ 2, J ≤ 45 and K ≤ 20) has been generated from the model giving essentially complete coverage of observable CH(3)(32)SH transitions within the bandwidths of major new astronomical facilities such as HIFI (Heterodyne Instrument for the Far Infrared) on the Herschel Space Observatory, ALMA (Atacama Large Millimeter Array), SOFIA (Stratospheric Observatory For Infrared Astronomy) and APEX (Atacama Pathfinder Experiment) to close to spectroscopic accuracy.
在这项工作中，我们研究了甲硫醇（CH(3)SH）的太赫兹和傅里叶变换远红外（FTFIR）同步辐射光谱，以便为在星际分子云和恒星形成区中增强对该物种的观测提供新的实验室信息。像它的甲醇同类物一样，甲硫醇具有特别丰富的光谱，与它的大振幅内部旋转有关，这些光谱延伸到太赫兹和远红外区域。我们在科隆大学记录了 CH(3)SH 的新光谱，频率范围为 1.1-1.5 和 1.790-1.808 太赫兹，以及在加拿大光源的远红外光束线上以 0.001 厘米（-1）的分辨率记录了 50-550 厘米（-1）的高分辨率 FTFIR 同步辐射光谱。报告了旋转量子数高达 J ≈ 40 和 K ≈ 15 以及扭转态高达 v(t) = 2 的旋转量子数和 v(t) = 3 的 FTFIR 观测的 assignments。太赫兹和 FTFIR 测量结果与文献结果相结合，对包括总共 1725 个微波和太赫兹频率以及约 18000 个 FTFIR 跃迁的数据集进行了全局分析，这些跃迁的范围高达 v(t) = 2 和 J(max) = 30 对于 MW∕THz 和 FTFIR 的 40。全局拟合采用了 78 个扭转-旋转参数，达到了约 1.1 的加权标准偏差。从模型中生成了一个预测列表（v(t) ≤ 2，J ≤ 45 和 K ≤ 20），该列表基本上完全覆盖了主要新天文设施（如赫歇尔太空天文台的 HIFI（远红外外差仪器）、ALMA（阿塔卡马大型毫米阵列）、SOFIA（平流层观测红外天文学）和 APEX（阿塔卡马探路者实验））的带宽内可观测的 CH(3)(32)SH 跃迁的带宽接近光谱精度。
