Spectra of doubly deuterated propylene oxide, ${\mathrm{CH}}_3{\mathrm{CHCD}}_2\mathrm{O}$, were recorded in the millimeter-wave spectral region up to 330 GHz utilizing a 2f frequency modulated Terahertz spectrometer. Rotational and centrifugal distortion constants and tunneling parameters for the description of the internal rotation of the methyl group were retrieved. The software XIAM was used to describe the A–E tunneling splitting with a frequency uncertainty of 82 kHz. Molecular parameters derived from our measurements are complemented by quantum chemical anharmonic frequency calculations on the B3LYP/aug-cc-pVTZ level of theory. In addition, the barrier height to internal rotation of the methyl group, $V_3$, was derived experimentally and found to slightly differ from the value reported for the main isotopologue. In view of astrophysical observations we provide accurate line lists to search for doubly deuterated propylene oxide in space. Furthermore, we deliver improved molecular parameters to further investigate the properties of a simple chiral molecule possessing internal large amplitude motions.

双氘化环氧丙烷的光谱， ${\mathrm{CH}}_3{\mathrm{慢性病防治中心}}_2\mathrm{哦}$， 使用2f调频太赫兹光谱仪在高达 330 GHz的毫米波光谱区域中记录。检索了用于描述甲基内部旋转的旋转和离心变形常数和隧道参数。软件 XIAM 用于描述频率不确定性为 82  kHz的 A-E 隧道分裂。从我们的测量中得出的分子参数得到了 B3LYP/aug-cc-pVTZ 理论水平上的量子化学非谐频率计算的补充。此外，甲基内旋的势垒高度，${伏}_3$, 是通过实验得出的，发现与主要同位素体的报告值略有不同。鉴于天体物理观测，我们提供了准确的线列表以在太空中搜索双氘化环氧丙烷。此外，我们提供了改进的分子参数，以进一步研究具有内部大振幅运动的简单手性分子的性质。