Far-wing excitation study of the reactions in the Hg-H₂ collisional quasimolecules. II. Rovibrational distributions of HgH, HgD (X²∑⁺) formed from Hg-H₂, D₂, HD

We have applied the laser-pump/probe and double-beam absorption/dispersion approaches to the far wings of the Hg ³P₁-¹S₀ resonance line broadened by collisions with H₂, D₂, and HD. Absolute reduced absorption coefficients of the Hg-D₂ quasimolecules have been determined as a function of the wave-number shift A from the resonance-line center both in the red and blue wings. The nascent rotational distributions have been determined for the υ =0 and 1 levels of HgH (X ²∑⁺) and the υ =0 level of HgD (X ²∑⁺) formed from the Hg*(³P₁)-H₂, D₂, and HD collisional-quasimolecular states à and B̃ attained by the red- and blue-wing excitation, respectively. Both of the intermediate states à and B̃ give quite similar rotational distributions peaking around N ≃ 18 for HgH and N-25 for HgD insensitive to the excitation-wave-number shift A. 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-D₂ 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 A 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 and B states. The different type of transition state, however, may be encountered on the pathways producing the minor components in the low-N levels.