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Updated: Oct 17, 2025

Direct Imaging of Laser-driven Ultrafast Molecular Rotation
Published on: February 4, 2017
Rotational (de)-excitation of C5 by collision with He at low temperature
A Chefai1, M Ben Khalifa1, F Khadri1
1Laboratory of Atomic Molecular Spectroscopy and Applications, Department of Physics, Faculty of Sciences, University Tunis El Manar, Campus Universities 1060, Tunis, Tunisia. chefai.atka@fst.utm.tn.
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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