Isotopic effects on the rotational (de-)excitation rate coefficients of ortho-CH3Cl colliding with He.

Chloromethane, CH3Cl, is the first organohalogen molecule to be detected in the interstellar medium. Using the recently generated accurate three-dimensional potential energy surface (3D-PES) for the weakly bound CH335Cl-He complex, we deduced that of CH337Cl-He. Both 3D-PESs were incorporated later into dynamical computations code for nuclear motions treatments of each isotopologue colliding with He.

Collision excitation of c-CH(XA) by He.

Accurate modeling of anionic abundances in the interstellar and circumstellar media requires calculations of collisional data with the most abundant species that are usually He atoms and H molecules. In this paper, we focus on smaller cyclic molecular anion, c-CH, an astrophysical candidate, following the detection of larger CH carbon chains. From a new three-dimensional potential energy surface, the rotational (de-)excitation of the c-CH(XA) anion by collision with He is investigated.