Mercury halide spectroscopy

The B−X, C−X, and D−X transitions of HgCl, HgBr, and HgI are reanalyzed using Tesla discharge sources containing single isotopic species of these molecules. Direct, simultaneous least‐squares fits of all transitions yield optimal vibrational constants for all four states. Low‐resolution studies of the emission as a function of buffer gas pressure show effects of vibrational relaxation in the B state and collisional quenching of the C and D states. The broad B−A bands in the red and infrared are weak but clearly present, in support of a recent report of this transition in HgBr. In addition there is evidence of other transitions, previously unreported for these molecules, including a very weak system near 2200 A in HgI, which shows fine red‐degraded vibrational band structure.