Desrousseaux Benjamin, Lique François
LOMC - UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 1123, F-76063 Le Havre, France.
J Chem Phys. 2020 Feb 21;152(7):074303. doi: 10.1063/1.5142655.
The HeH molecule is the first to be formed in the Universe. Its recent detection, in the interstellar medium, has increased the interest in the study of the physical and chemical properties of this ion. Here, we report exact quantum time-independent calculations of the collisional cross sections and rate coefficients for the rotational excitation of HeH by H. Reactive and exchange channels are taken into account in the scattering calculations. Cross sections are computed for energies of up to 10 000 cm, enabling the computation of rate coefficients for temperatures of up to 500 K. The strongest collision-induced rotational HeH transitions are those with Δj = 1. Previous results obtained using approximate treatment are compared to the new ones, and significant differences are found. The new rate coefficients are also compared to those for electron-impact rotational excitation, and we found that collisions with H dominate the excitation of HeH in media where the electron fraction is less than 10. In the light of those results, we recommend the use of the new HeH-H collisional data in order to accurately model HeH excitation in both the interstellar media and early Universe.
HeH分子是宇宙中最早形成的分子。最近在星际介质中对其进行的探测，增加了人们对研究该离子物理和化学性质的兴趣。在此，我们报告了H与HeH碰撞激发转动的碰撞截面和速率系数的精确量子定态计算。散射计算中考虑了反应和交换通道。计算了能量高达10000 cm⁻¹时的截面，从而能够计算温度高达500 K时的速率系数。碰撞诱导的HeH最强转动跃迁是那些Δj = 1的跃迁。将先前使用近似处理得到的结果与新结果进行了比较，发现存在显著差异。还将新的速率系数与电子碰撞转动激发的速率系数进行了比较，我们发现，在电子分数小于10⁻⁷的介质中，与H的碰撞主导了HeH的激发。鉴于这些结果，我们建议使用新的HeH-H碰撞数据，以便在星际介质和早期宇宙中准确模拟HeH的激发。
