Rotational Excitation Cross Sections for Chloronium Based on a New 5D Interaction Potential with Molecular Hydrogen

Chloronium (H2Cl+) is an important
intermediate
of Cl-chemistry in space. The accurate knowledge of its collisional
properties allows a better interpretation of the corresponding observations
in interstellar clouds and, therefore, a better estimation of its
abundance in these environments. While the ro-vibrational spectroscopy
of H2Cl+ is well-known, the studies of its collisional
excitation are rather limited and these are available for the interaction
with helium atoms only. We provide a new 5-dimensional rigid rotor
potential energy surface for the interaction of H2Cl+ with H2, calculated from explicitly correlated
coupled cluster ab initio theory, which was fitted
then with a set of analytical functions, allowing to perform scattering
calculations using accurate quantum theories. We analyze the collision-energy
dependence of the rotational state-to-state cross sections and the
temperature-dependence of the corresponding thermal rate coefficients,
with particular attention on the collisional propensity rules. When
comparing our results for collisions with H2 with those
obtained with He as a colliding partner, we found very significant
differences with nonlinear scaling trends, which proves again that
He is not a suitable proxy for collisions between hydride molecules
and molecular hydrogen, the most abundant gas particle in the interstellar
medium.