The reasons for the discrepancies between the experimental data on the shape of long-wavelength continua near the 6^3 P _1 → 6^1 S _0 resonance line of a mercury atom in a xenon atmosphere obtained by different authors are analyzed. Calculations of spectral profiles for limiting cases of high and low densities of buffer gas atoms lead to the conclusion that the discrepancies are mainly due to the dependence of the rates of three-particle recombination and relaxation processes on the xenon density. Different types of a non-equilibrium or almost equilibrium (at high xenon concentrations) population of rovibrational states of a HgXe( A ^30^+) excimer molecule are formed at different rates of these processes, which affects emission spectral profiles.