Coding Cross Sections of an Electron Charge Transfer Process

The paper presents the algorithm of a code written for computing the cross section for a charge transfer process involving a neutral molecule and a monatomic ion. The entrance and exit potential energy surfaces, driving the collision dynamics, are computed employing the Improved Lennard-Jones function that accounts for the role of nonelectrostatic forces, due to size repulsion plus dispersion and induction attraction. In addition, electrostatic components, affecting the entrance channels, are evaluated as sum of Coulomb contributions, determined by the He+ ion interacting with the charge distribution on the molecular frame. The cross section is estimated by employing the Landau- Zener-St¨uckelberg approach. The code implemented has been employed in systems involving helium cation and a small organic molecule, such as methanol, dimethyl ether and methyl formate.