We have applied the laser-pump/probe and double-beam absorption/dispersion approaches to the far wings of the Hg P-3(1)-S-1(0) resonance line broadened by collisions with H-2, D-2, and HD. Absolute reduced absorption coefficients of the Hg-D-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, The nascent rotational distributions have been determined for the v = 0 and 1 levels of HgH (X (2) Sigma(+)) and the v = 0 level of HgD (X (2) Sigma(+)) formed from the Hg*(P-3(1))-H-2, D-2, and HD collisional-quasimolecular states (A) over tilde and (B) over tilde attained by the red- and blue-wing excitation, respectively. Both of the intermediate states (A) over tilde and (B) over tilde give quite similar rotational distributions peaking around N similar or equal to 18 for HgH and N similar or equal to 25 for HgD insensitive to the excitation-wave-number shift Delta. However, a small difference is found : the red-wing excitation gives larger populations in the low-N levels than the blue-wing one. The departing atom isotope effect is observed in these low-N populations of HgD from Hg-D-2 and Hg-HD. The absolute ratio of the nascent yields of v = 1 to 0 has been measured to be 0.3, being nearly constant against Delta in both the red and blue wings, These observations indicate that HgH is formed predominantly from a bent H-Hg-H configuration on both the pathways via the (A) over tilde and (B) over tilde states. The different type of transition state, however, may be encountered on the pathways producing the minor components in the low-N levels.