Adiabatic Potential Energy Surfaces for the Low-Energy Collisional Dynamics of C+(P-2) Ions with H-2 Molecules

The low-energy electronic states of the CH2+ molecular ion are investigated with multireference configuration interaction calculations based on complete active space self-consistent field reference wave functions using a large C(6s5p4d3f)/H(8s6p3d1f) basis set. The focus is on the three lowest-lying states describing formation and destruction of the astrophysically relevant methylidine cation CH+. Both processes are discussed in light of the topology of the relevant potential energy surfaces and their intersections.