The IR spectra of liquid hydrogen isotopologues (Q₂ = H₂, D₂, T₂, HD, HT, DT) are dominated by the interaction induced absorption. Therefore, the complexity tremendously increases with the number of different isotopologues in the sample. As we aim for a system independent calibration of IR absorption spectroscopy against all six isotopologues and three ortho–para ratios, we need a minimal and complete set of descriptors to predict the spectra and to decrease the needed calibration effort. For this, we grouped the absorption lines into three groups: absorption on monomers, phonons, and molecular dimers. In particular, molecular dimers contribute to the absolute number of absorption lines in the spectra of mixed isotopologues. To develop and test the set of descriptors, we make use of three spectra: a pure H₂ sample, a pure D₂ sample, and a mixed H₂–D₂ sample. We show a detailed analysis of these three spectra in the first and second vibrational branch in the range from 2000 cm⁻¹ to 9000 cm⁻¹. The set of descriptors found within this work can be used to identify and predict all lines in this range for liquid H₂–D₂mixtures.

中文翻译：

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液态H2-D2混合物的红外吸收光谱的最小和完整的描述符集

液态氢同位素同位素（Q ₂ = H ₂，D ₂，T _2）的红外光谱，HD，HT，DT）被相互作用诱导的吸收所支配。因此，复杂度随着样品中不同同位素分子的数量而大大增加。由于我们的目标是针对所有六个同位异构体和三个邻对位比对系统进行红外吸收光谱的系统独立校准，因此我们需要一套最小和完整的描述符来预测光谱并减少所需的校准工作。为此，我们将吸收线分为三类：单体，声子和分子二聚体的吸收。特别地，分子二聚体在混合的同位素异构体的光谱中有助于吸收线的绝对数量。为了开发和测试描述符集，我们使用三个光谱：纯H ₂样品，纯D ₂样品和混合H₂ –D ₂样本。我们显示了在从2000 cm ^-1到9000 cm ^-1的范围内的第一和第二振动分支中这三个光谱的详细分析。在这项工作中发现的描述符集可用于识别和预测液态H ₂ -D ₂混合物在此范围内的所有谱线。