LAUSR

Collisions between H2 and H are crucial to the thermal balance of astrophysical media, especially that of the early Universe. We report Quasi-Classical Trajectory (QCT) calculations of rate coefficients for the collisional (de-)excitation of H2 by H – including the three-body collisional dissociation – on a highly accurate H3 potential energy surface (PES). Translational temperatures ranging from 100 to 15 000 K, and ro-vibrational energy levels of H2 up to ≈50 000 K are considered. Our QCT rate coefficients agree well with those obtained from previous quantum calculations on the same PES. This good agreement supports our claim that, in order to study the 5000 to 15 000 K temperature range, typical of the early Universe, inexpensive QCT calculations should be preferred to extrapolation of costly quantum calculations run at lower temperatures. The new collisional rate coefficients should enhance our ability to model the cooling and heating budget of the primordial gas.