We report a study of the time evolution of differentgroupsof HgBr (X2&Sgr;+1/2) vibrational level densities which are quenched by collisions with He. Vibrational quenching is efficient down to the lowestv″levels that we are able to monitor, indicating that energy can be efficiently extracted from the HgBr (B→X) laser, even when tuning to frequencies other than those with the highest gain.