Millimetre wave spectrum of methyl mercaptan

An investigation of the rotational spectrum of CH 3 32 SH, one of the most recent molecules to be detected in the interstellar medium, has been carried out over the 25–107 GHz region. The frequencies of a-type Δk = 0 R-branch transitions have been measured for the J = 1 ← 0 up to J = 4 ← 3 multiplets for torsional states ν t = 0–3. In addition, many P-, Q-, and R-branch transitions with Δk ≠ 0 have been identified in order to provide a catalogue of lines for potential radio astronomical applications. Improved values of rotational and centrifugal distortion constants, a-type torsion–vibration–rotation interaction constants, and torsional barrier parameters (V 3 = 444.76 cm −1 ; effective V 6 = −2.07 cm −1 ) have been determined from least-squares analyses of the spectra.