AI 中文总结
研究星际介质中甲酸异构体丰度，用显式相关耦合簇理论计算其与氦原子相互作用的势能面，得到全局最小值，计算碰撞激发截面，显示相似倾向规则并讨论定量差异。
AI 中文摘要
准确估计星际介质中异构体的分子丰度对于揭示潜在的化学和物理过程至关重要。在最近在致密暗冷云中检测到甲酸的两种异构体（顺式和反式HCOOH）之后，它们精确的分子线建模变得很有意义。这些环境条件不一定遵循局部热力学平衡，因此需要考虑辐射和碰撞过程之间的竞争。这涉及到与星际中最丰富的物种He和H₂碰撞的转动激发数据。本文使用显式相关耦合簇理论[CCSD(T)-F12]计算了甲酸两种旋转异构体与He原子相互作用的第一势能面（PES）。得到的PES显示出定性相似性和高各向异性。顺式-HCOOH和反式-HCOOH的全局最小值分别为V = -53.0 cm⁻¹和V = -46.0 cm⁻¹。计算了高达100 cm⁻¹总能量的碰撞激发截面，显示了两种异构体相似的倾向规则，还讨论了与两种旋转异构体相关截面的定量差异。
英文摘要
An accurate estimation of the molecular abundances of isomers in the interstellar medium (ISM) is necessary to unravel the underlying chemistry and physics. After the recent detections of both isomers of formic acid ($cis-$ and $trans-$HCOOH) in dense dark cold clouds, their accurate molecular line modeling became of interest. The conditions of these environments do not necessarily follow the local thermodynamic equilibrium, thus taking into account the competition between the radiative and collisional processes is required. This involves the knowledge of the rotational excitation data for collisions with the most abundant interstellar species \textemdash He and H$_2$. In this paper, the first potential energy surfaces (PES) for the interaction of the two rotamers of formic acid with He atoms are computed using the explicitly correlated coupled-cluster theory [CCSD(T)-F12]. The obtained PESs demonstrate qualitative similarities and high anisotropy. The global minima are found with $V=-53.0$ cm$^{-1}$ and $V=-46.0$ cm$^{-1}$ for $cis-$HCOOH and $trans-$HCOOH respectively. Collisional excitation cross sections calculated for total energies up to 100 cm$^{-1}$ demonstrate similar propensity rules for both isomers. Quantitative differences of the cross sections associated with the two rotamers are also discussed.
