Laser-pump/probe and double-beam absorption/dispersion approaches have been applied to the far wings of the Hg P-3(1)-S-1(0) resonance line broadened by collisions with H-2, Absolute reduced absorption coefficients of the Hg-H-2 quasimolecules have been determined as a function of the wave-number shift Delta from the resonance-line center both in the red and blue wings. Decay probabilities of the excited Hg*(P-3(1))-H-2 quasimolecule into the reactive channel (HgH formation) or into the elastic channel (Hg*(P-3(1)) formation) have been determined as a function of Delta both for the red-wing excited (A) over tilde and blue-wing excited (B) over tilde states. The rest of these decay probabilities have been attributed to three-body dissociation Hg(S-1(0))+H+H. These results indicate that (a) the (A) over tilde-state surface serves more effectively in HgH formation than the (B) over tilde-state surface by a factor of about 2.3; but (b) three-body dissociation, in turn, proceeds far more efficiently on the (B) over tilde-state surface than on the (A) over tilde-state surface, Discussions about the energy barriers and the orbital correlations for HgH formation are presented, based on the Delta dependence of these decaying probabilities.