We present one of the first Shanghai Tian Ma Radio Telescope (TMRT) K Band observations towards a sample of 26 infrared dark clouds (IRDCs). We observed the (1,1), (2,2), (3,3), and (4,4) transitions of NH₃ together with CCS (2₁–>1₀) and HC₃N J = 2–1, simultaneously. The survey dramatically increases the existing CCS-detected IRDC sample from 8 to 23, enabling a better statistical study of the ratios of carbon-chain molecules (CCM) to N-bearing molecules in IRDCs. With the newly developed hyperfine group ratio (HFGR) method of fitting NH₃ inversion lines, we found the gas temperature to be between 10 and 18 K. The column density ratios of CCS to NH₃ for most of the IRDCs are less than 10⁻², distinguishing IRDCs from low-mass star-forming regions. We carried out chemical evolution simulations based on a three-phase chemical model NAUTILUS. Our measurements of the column density ratios between CCM and NH₃ are consistent with chemical evolutionary ages of ≲10⁵ yr in the models. Comparisons of the data and chemical models suggest that CCS, HC₃N, and NH₃ are sensitive to the chemical evolutionary stages of the sources.

我们展示了上海天马射电望远镜 (TMRT) K 波段对 26 个红外暗云 (IRDC) 样本的首批观测结果之一。我们观察到 NH ₃的 (1,1)、(2,2)、(3,3) 和 (4,4) 跃迁以及 CCS (2 ₁ –>1 ₀ ) 和 HC ₃ N J = 2– 1、同时。该调查将现有的 CCS 检测到的 IRDC 样本从 8 个显着增加到 23 个，从而能够更好地统计研究 IRDC 中碳链分子 (CCM) 与含氮分子的比率。与嵌合NH的新开发的超精细组比（HFGR）方法₃反转线，我们发现的气体温度为在10和K 18至NH CCS的柱体密度的比率₃对于大多数 IRDC 小于 10 ^-2，将 IRDC 与低质量恒星形成区区分开来。我们基于三相化学模型 NAUTILUS 进行了化学演化模拟。我们对CCM 和NH ₃之间的柱密度比的测量与模型中≲10 ⁵ yr 的化学演化年龄一致。数据和化学模型的比较表明 CCS、HC ₃ N 和 NH ₃对源的化学演化阶段很敏感。