In this work, we studied the helium-induced collisional excitation of the radical ion HCl+. Our work focuses on calculating two-dimensional potential energy surfaces (PES) to study the interaction due to the collision between HCl+ and He, and on analyzing the influence of the isotopic effect on cross sections and collision rates. For Ab initio calculations of PES $^{2}A^{\prime }$ and $^{2}A^{\prime \prime }$ of HCl+(X $^{2}\Pi $ )-He complex, we used the RCCSD(T)-F12 method with cc-pVQZ-F12 basis sets. These surfaces have been fitted using the Reproducing Kernel Hilbert Space (RKHS) method and were submitted to the close-coupling approach in order to work out the inelastic integral cross sections. Collision cross sections taking into account the fine structures of HCl+ have been performed for kinetic energies up to 3500 cm−1 and the thermal excitation rates for kinetic temperatures varying from $4K$ up to 400 K. It appears that the difference in the cross section and collisional rate cofficients for the H35Cl+ and H37Cl+ colliding with He was found to be negligeable. In contrast, a significant difference in effective cross-sections and collision rates between HCl+-He and DCl+-He was observed to the extent that it is impossible to make estimation of collision rates of deuterated species from those of the hydrogenated species.
