The absorption and emission spectra of the 3P1-1S0 transition of a Hg atom embedded in solid Ar were simulated using the mol. dynamics with quantum transitions algorithm to consider the nonadiabatic transitions between the three adiabatic states. The simulations also take into account the zero-point fluctuations at the exptl. temp. of 4 K using a temp. correction that mimics them. The simulated spectra show fair agreement with the exptl. data for the abs. energies and very good agreement for the absorption-emission Stokes shift. The absorption band consists of the contribution due to absorption of the three degenerate at. states. The simulations of the emission spectrum, with inclusion of nonadiabatic couplings, lead to a single emission band stemming from the lowest adiabatic surface. When running the simulations without consideration of the nonadiabatic coupling, the simulated absorption and emission spectra exhibit three bands sepd. by hundreds of cm-1, in total disagreement with the expt. Photoexcitation of Hg(3P1) in Ar matrixes was characterized by the medium-induced nonadiabatic couplings among its adiabatic states. [on SciFinder (R)]