Abstract
CH+ is an important reactive molecular ion in the interstellar medium with photodissociation properties that are essential for understanding its formation and destruction in UV-irradiated environments. In this work, high-level MRCI+Q calculations were performed for 18 singlet and triplet states correlating with the six lowest dissociation limits. The resulting potential energy curves, transition dipole moment curves, spin–orbit couplings, and electronic angular momentum couplings were employed to calculate the internal partition functions and the rovibrationally resolved photoabsorption and direct photodissociation cross sections. The results show that photoabsorption by CH+ is dominated by the bound–bound X1Σ+–A1Π transition system, whereas photodissociation is primarily controlled by transitions from the ground state to repulsive excited states, with the X1Σ+–E1Σ+ and X1Σ+–C1Σ+ channels providing the dominant contributions. The positions of the principal photodissociation features are generally consistent with those reported in the Leiden database. Using the cross sections evaluated under local thermodynamic equilibrium, we further determined the photodissociation rates of CH+ under the standard interstellar radiation field and blackbody radiation conditions. The calculated rates exhibit a pronounced dependence on molecular temperature. These results provide valuable molecular data for astrochemical modeling of CH+ activity in ultraviolet-irradiated environments.