Abstract In the context of radio-astronomical observations, laboratory experiments constitute a cornerstone in the interpretation of rich line surveys due to the concomitant presence of numerous emitting molecules. Here, we report the investigation of three different rotational transitions of mono-deuterated ammonia (NH2D), a species of astrophysical interest, for which the contribution of the deuterium nuclear spin to the rotational spectrum has been resolved for the first time in the millimeter- and submillimeter-wave domain. The effect of hyperfine interactions on the rotational spectrum has been unveiled by a combined theoretical and experimental approach. Quantum-chemical calculations based on coupled-cluster theory have been employed to evaluate the hyperfine parameters of nitrogen, hydrogen, and deuterium in NH2D. Subsequently, the Lamb-dip technique has been used to investigate the rotational spectrum of NH2D at high-resolution. In detail, three low-J transitions have been recorded at 86, 110, and 333 GHz with a frequency-modulation millimeter-/submillimeter-wave spectrometer. From the line profile analysis of the recorded spectra, the main terms responsible for the rotational hyperfine structure have been determined with good accuracy. Our work allows a comprehensive analysis of the rotational features of NH2D in radioastronomical spectra and a more accurate evaluation of its column density, especially in non-turbulent regions showing narrow linewidths.

中文翻译：

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Lamb-dip 光谱揭示的 NH2D 旋转光谱中的氘超精细分裂

摘要 在射电天文观测的背景下，由于大量发射分子的伴随存在，实验室实验构成了解释丰富线勘测的基石。在这里，我们报告了对单氘氨 (NH2D) 的三种不同旋转跃迁的研究，NH2D 是一种天体物理学感兴趣的物种，其中氘核自旋对旋转光谱的贡献首次以毫米为单位解决。和亚毫米波域。超精细相互作用对旋转光谱的影响已通过理论和实验相结合的方法得以揭示。基于耦合簇理论的量子化学计算已被用于评估 NH2D 中氮、氢和氘的超精细参数。随后，Lamb-dip 技术已被用于高分辨率研究 NH2D 的旋转光谱。详细地说，已经使用调频毫米波/亚毫米波光谱仪在 86、110 和 333 GHz 记录了三个低 J 跃迁。从记录光谱的线轮廓分析中，已经以良好的精度确定了负责旋转超精细结构的主要术语。我们的工作允许对射电天文光谱中 NH2D 的旋转特征进行全面分析，并更准确地评估其柱密度，尤其是在显示窄线宽的非湍流区域。和 333 GHz 频率调制毫米波/亚毫米波光谱仪。从记录光谱的线轮廓分析中，已经以良好的精度确定了负责旋转超精细结构的主要项。我们的工作允许对射电天文光谱中 NH2D 的旋转特征进行全面分析，并更准确地评估其柱密度，尤其是在显示窄线宽的非湍流区域。和 333 GHz 频率调制毫米波/亚毫米波光谱仪。从记录光谱的线轮廓分析中，已经以良好的精度确定了负责旋转超精细结构的主要项。我们的工作允许对射电天文光谱中 NH2D 的旋转特征进行全面分析，并更准确地评估其柱密度，尤其是在显示窄线宽的非湍流区域。