Derivation of diabatic potentials for F + H2 employing non-adiabatic coupling terms

We present a study of the non-adiabatic coupling terms (NACTs) and the corresponding diabatic potentials for the reactive H2 + F system in the entrance channel. The study reveals two conical intersections (ci): (I) A Jahn–Teller (1, 2) ci, located at a point on the collinear HHF axis close to the minimum energy path; (II) A Renner–Teller line of (2, 3) cis, along the collinear HHF axis. To form the diabatic potentials we consider only the two lower adiabatic potentials and the quantized Born–Oppenheimer mixing angles that guarantee single-valued diabatic potentials.