Collision-induced quasimolecular radiation was experimentally and theoretically investigated near the spin-forbidden line Hg(6 ³P₂ - 6 ¹S₀) in thermal collisions with argon atoms. The mechanism of removing for prohibition at a quantitative level can be understood in the framework of the intermediate, between “a” and “c” Hund's coupling cases. For the first time, the experimental spectrum of quasimolecular radiation was obtained for the system in question, and the comparison with theoretical results obtained earlier was carried out. The temperature dependence of the radiative decay rate of the mercury atom metastable state in collisions with argon atoms was also obtained.