We have investigated the elementary processes occurring in H-2 + H-2 collis
ions by integrating large batches of quasiclassical trajectories. This has
allowed us to calculate the vibrational state-selected rate coefficients as
well as their aggregations in classes leading to the same products and the
ir dependence on temperature. The contribution of the Various elementary an
d aggregated processes both to the allocation of energy among the various v
ibrational states of the products and to the production of hydrogen atoms i
s analyzed. Some correlations of these contributions with the value of the
impact parameter and with some characteristics of the reactive mechanism ar
e also discussed; The key importance of hydrogen exchange processes is also
singled out.