Similar to ethane (C₂H₆), monodeuterated ethane (C₂H₅D) has a bright series of Q-branches in the CH stretch region, between about 2960 - 3020 cm${}^{-1}$ (3.38 - 3.31 µm). As the progressions in the different isotopes are slightly offset from one another, the new C₂H₅D model enables sensitive constrains of the D/H ratio in spectra from comets, in organics across the Solar System and beyond. Specifically, the D/H ratio of organic molecules in comets is a critical cosmogenic indicator, which not only provides insights into the formation processes of our Solar System, but also allows for a test of our understanding of solid-state astrochemistry. High D/H ratios are predicted in a number of astrochemical models, which can be benchmarked using the new spectroscopic information of C₂H₅D and C₂H₆. We present a quantum band model for C₂H₅D in the mid-infrared. Our model is based on rotationally resolved spectra of C₂H₅D and C₂H₆ obtained at 85K between 2050 - 3050 cm${}^{-1}$ (4.88 - 3.28 µm) using a Bruker IFS-125HR equipped with a cryogenic Herriott cell at JPL. High-level quantum chemical calculations were carried out at the CCSD(T)/ANO1 level of theory to aid vibrational assignments, with the anharmonic frequencies and vibrational corrections determined from second-order vibrational perturbation theory (VPT2). As a first demonstration of the applicability of the model, we obtained a stringent upper limit to the organic D/H ratio (18.2 VSMOW) in comet C/2007 W1 (Boattini) from high resolution fluorescence spectra obtained with Keck/NIRSPEC.

与乙烷（C ₂ H ₆）相似，单氘代乙烷（C ₂ H ₅ D）在CH拉伸区具有一系列明亮的Q支，大约2960-3020 cm${}^{-\mathrm{1个}}$（3.38-3.31 µm）。由于不同同位素的进展彼此之间略有偏移，因此新的C ₂ H ₅ D模型可对彗星，整个太阳系及其他有机物中的光谱中的D / H比进行敏感的约束。具体来说，彗星中有机分子的D / H比是一个重要的宇宙成因指标，它不仅可以洞察太阳系的形成过程，还可以测试我们对固态天化学的理解。在许多天化学模型中预测到高的D / H比，可以使用C ₂ H ₅ D和C ₂ H ₆的新光谱学信息进行基准测试。我们提出了C的量子带模型₂ H ₅ D在中红外。我们的模型基于2050-3050 cm之间在85K下获得的C ₂ H ₅ D和C ₂ H _6的旋转分辨光谱${}^{-\mathrm{1个}}$（4.88-3.28 µm），使用JPL装有低温Herriott池的Bruker IFS-125HR。在CCSD（T）/ ANO1的理论水平上进行了高级量子化学计算，以帮助进行振动分配，并根据二阶振动摄动理论（VPT2）确定了非谐频率和振动校正。作为该模型适用性的第一个证明，我们通过由Keck / NIRSPEC获得的高分辨率荧光光谱，获得了彗星C / 2007 W1（Boattini）中有机D / H比的严格上限（18.2 VSMOW）。