TheB → Xspectra of HgCl and HgI are studied at high resolution for the single isotopic species,200Hg35Cl,200Hg127I, and200Hg129I. For HgI the analysis indicates that thev″ numbering should be decreased by one unit from the previous assignment. For both molecules the analyses deviate progressively from the previous assignments at highv″, extrapolating to lower estimates of the ground‐state dissociation energies. Franck–Condon calculations yield &Dgr;Re(=Re′ −Re″) =0.60A˚ for HgCl and 0.49 A˚ for HgI. The strongest laser features previously reported for HgCl occur near the heads of the overlapped 0–22, 1–23, 2–24, and 3–25 bands. The HgI laser operates in the region of the 0–14, 0–15, 1–15, 1–16, 2–17, and 2–18 bands.