Revisited study of the ro-vibrational excitation of H2 by H: Towards a revision of the cooling of astrophysical media

Abstract

We report nearly exact quantum time-independent calculations of rate coefficients for the collisional (de-)excitation of H2 by H, from low to high temperatures. Our calculations are based on a highly accurate global potential energy surface. The reactive hydrogen exchange channels are taken into account rigorously. New collisional data are obtained for the rovibrational relaxation of highly excited H2 (with internal excitation up to ≃22 000 K) for temperatures ranging from 100 to 5000 K. We also provide a comparison with the available experimental rate coefficients at room temperature. The good agreement between theory and experiment is an illustration of the accuracy of the present calculations. The new results significantly differ from previous data presently used in astrophysical models, especially at low temperatures, the difference being essentially due to the inclusion of the reactive channels. The impact of these new data in astrophysics is discussed. In particular, the coolingmechanism will have to be reviewed for several astrophysical media.