Molcol: A program for solving atomic and molecular collision problems Original Research Article

We describe a Fortran program that enables cross sections to be calculated for collisions between two systems of arbitrary angular momenta. The quantal coupled channels (partial wave expansion) method is used. Illustrative results are presented for the case of a collision between an atom (He 1s 2 1 S) and a vibrating diatomic molecule (H 2 ), and between a molecule (H 2 ) and an atom possessing fine structure (O 1s 2 2s 2 2p 4 3 P).