The infrared Fourier transform spectrum of the lower vibrational modes of the CD₃SH isotopologue of methyl mercaptan has been recorded using synchrotron radiation at the FIR beamline of the Canadian Light Source. Torsion-rotation structure has been analyzed for a strong parallel band centred at 644 cm⁻¹ and a weaker perpendicular band centred at 727 cm⁻¹, identified respectively with a mixed {in-plane-CD₃-rocking/CSH-bending} mode and the out-of-plane CD₃ rock. The torsional energies for the latter mode follow well-behaved curves, inverted with respect to the ground state, but those for the former do not display a systematic pattern. Surprisingly, no clear evidence was seen for the C-S stretching fundamental band, in contrast to CH₃SH and the analogous CD₃OH and CH₃OH methanol species for which the corresponding C-S or C-O stretching bands are major features of the spectrum. This mystery prompted an ab initio calculation to compare the CD₃SH and CH₃SH vibrational frequencies and transition moments. A mode lying in the expected position was indeed predicted for CD₃SH but with almost vanishing intensity. The calculated reduced mass and effective force constant for this mode corresponded closely to those for the C-S stretch of normal CH₃SH, indicating that an anticipated strong C-S stretching band is in fact almost completely extinguished for CD₃SH.

在加拿大光源的 FIR 光束线上使用同步辐射记录了甲硫醇的 CD ₃ SH 同位素体的较低振动模式的红外傅立叶变换光谱。^{已针对以 644 cm -1为中心的强平行带和以 727 cm -1}为中心的较弱垂直带分析了扭转旋转结构，分别用混合{面内-CD ₃ -摇摆/CSH-弯曲}模式识别和平面外 CD ₃岩石。后一种模式的扭转能量遵循良好的曲线，相对于基态反转，但前者的扭转能量没有显示系统模式。_{令人惊讶的是，与 CH 3} SH 和类似的 CD ₃ OH 和 CH ₃ OH 甲醇物质相比，没有看到 CS 伸缩基带的明确证据，其中相应的 CS 或 CO 伸缩带是光谱的主要特征。这个谜团促使我们进行从头算计算，以比较 CD ₃ SH 和 CH ₃ SH 的振动频率和跃迁时刻。_{确实为 CD 3}预测了位于预期位置的模式SH 但强度几乎消失。该模式计算的约化质量和有效力常数与正常 CH ₃ SH 的 CS 拉伸的那些非常接近，表明预期的强 CS 拉伸带实际上几乎完全消失了 CD ₃ SH。