The N = 2-1 pure rotational transition of the ND radical (X3Sigma-) near 1 THz was measured with the Cologne terahertz spectrometer. The ND radical was produced in a dc discharge of a flowing mixture of deuterated ammonia and helium. Frequencies of five strong fine-structure transitions with associated hyperfine components were precisely measured and analyzed to determine a complete set of accurate molecular constants, e.g., the rotational and centrifugal distortion constants B0 = 263265.4735(45) MHz and D0 = 14.62876(74) MHz, together with the fine and hyperfine constants. Based on these constants, the rotational frequencies of ND up to 4 THz were predicted with the aim to guide future astronomical searches. For completeness we also include similar predictions for NH. Copyright 1998 Academic Press.

中文翻译：

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ND Radical：1 THz 频率下 N= 2–1 旋转跃迁的实验室测量

使用科隆太赫兹光谱仪测量 ND 自由基 (X3Sigma-) 在 1 THz 附近的 N = 2-1 纯旋转跃迁。ND 自由基是在氘化氨和氦的流动混合物的直流放电中产生的。精确测量并分析了五个具有相关超精细成分的强精细结构转变的频率，以确定一整套准确的分子常数，例如旋转和离心畸变常数 B0 = 263265.4735(45) MHz 和 D0 = 14.62876(74) MHz ，连同精细和超精细常数。基于这些常数，预测了 ND 高达 4 THz 的旋转频率，旨在指导未来的天文搜索。为完整起见，我们还包括对 NH 的类似预测。版权所有 1998 学术出版社。