Rotational (de-)excitation of CH3CN in collisions with H2 on an accurate potential energy surface

Observations of molecules with C3v symmetry, such as CH3CN, are particularly valuable in molecular clouds as the rotational transition selection rules of these molecules allow them to serve as gas thermometers. Interpreting their spectra in non-local thermodynamic equilibrium (non-LTE) conditions requires accurate collisional rate coefficients, especially for interactions with common interstellar species like H2. In this work, we present a five-dimensional potential energy surface for CH3CN in van der Waals interaction with H2 (1 Sigma+), computed using the CCSD(T)/F12 method and the aug-cc-pVTZ basis set. This potential energy surface is fitted with analytical functions suited for scattering calculations. Cross sections for rotational transitions in collisions between ortho- and para-CH3CN and para-H2 (j2 = 0) are computed using the close-coupling quantum scattering method, across energies from threshold up to 150 cm-1. These data are essential for interpreting interstellar CH3CN emission lines and advancing our understanding of diverse astronomical environments.