Reactive collisions of atoms with diatomic molecules

The theory of the reactive collision of an atom with a diatomic molecule is formulated in ‘‘democratic’’ hyperspherical coordinates. An adiabatic ansatz is used to separate the distance coordinate from the angular coordinates. The angular eigenvalue problem is solved, using the hyperspherical harmonics as basis functions, while the R-matrix propagation method is used to integrate the resulting coupled equations along the distance coordinate. As an example, reactive collision probabilities for H+H2 are computed, using the Porter–Karplus surface. The symmetry requirements, when dealing with three identical Fermions in the collision, are considered explicitly.