Coupled-channel calculation of differential cross sections for ionisation in proton collisions with molecular hydrogen

Accurate calculation of differential cross sections for ionisation in proton collisions with molecular hydrogen presents a significant challenge. Currently available results rely on perturbative methods and ignore coupling effects between the reaction channels, leading to poor agreement with experiment. We have developed a wave-packet convergent close-coupling method to calculate differential cross sections for ionisation in p+H₂ collisions. The approach expands the total scattering wave function in terms of both target and projectile-centred basis states. Substituting this expansion into the Schrödinger equation for the scattering system leads to a set of coupled differential equations to solve for the unknown expansion coefficients. The latter are then used to calculate the differential cross sections. The two-centre expansion allows us to determine direct ionisation and electron capture into the continuum of the projectile, both of which contribute significantly to the ionisation process at intermediate energies. Results for all types of the molecular orientation-averaged singly and doubly differential cross sections for single ionisation agree very well with experimental data where available, providing significant improvement on previously available calculations.