Chefai A, Ben Khalifa M, Khadri F, Hammami K. Rotational (de)-excitation of C
5 by collision with He at low temperature.
Phys Chem Chem Phys 2021;
23:23741-23747. [PMID:
34643208 DOI:
10.1039/d1cp02652f]
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Abstract
An appropriate estimation of the abundance of the observed C5 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 C5(X1Σ+)-He(X1S) 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 C5 by He were calculated for energies up to 1500 cm-1 using the standard (CC) method. The thermal dependence of the corresponding rate coefficients is given for the low and moderate temperature T ≤ 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 C5(X1Σ+) and modeling of carbon-rich media.
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