Chefai A, Ben Khalifa M, Khadri F, Hammami K
Laboratory of Atomic Molecular Spectroscopy and Applications, Department of Physics, Faculty of Sciences, University Tunis El Manar, Campus Universities 1060, Tunis, Tunisia.
Phys Chem Chem Phys. 2021 Oct 27;23(41):23741-23747. doi: 10.1039/d1cp02652f.
An appropriate estimation of the abundance of the observed C radical in the interstellar medium requires accurate radiative and collisional rate coefficients. We present the first two-dimensional potential energy surface (2D-PES) for the ground electronic state of the C(XΣ)-He(XS) van der Waals system, obtained using an explicitly correlated coupled-cluster method with single, double, and perturbative triple excitations (RCCSD(T)-F12). This PES is subsequently used in quantum close-coupling (CC) scattering calculations. Collisional excitation cross-sections of the rotational levels of C by He were calculated for energies up to 1500 cm using the standard (CC) method. The thermal dependence of the corresponding rate coefficients is given for the low and moderate temperature ≤ 300 K regime of interstellar molecular clouds. This is the first study on the collisional rate coefficients for this system and may have important implications for the astrophysical detection of C(XΣ) and modeling of carbon-rich media.
要准确估计星际介质中观测到的C自由基丰度，需要精确的辐射和碰撞速率系数。我们首次给出了C(XΣ)-He(XS)范德瓦尔斯体系基态电子态的二维势能面（2D-PES），该势能面是使用含单、双和微扰三重激发的显式相关耦合簇方法（RCCSD(T)-F12）得到的。随后，这个势能面被用于量子密耦（CC）散射计算。利用标准（CC）方法，计算了能量高达1500 cm时He对C转动能级的碰撞激发截面。给出了星际分子云低温和中温（≤ 300 K）区域相应速率系数的温度依赖性。这是对该体系碰撞速率系数的首次研究，可能对C(XΣ)的天体物理探测和富碳介质建模具有重要意义。
