Infrared spectra of the spherical top molecules XF6 (X = S, U, Mo, W) dissolved in liquefied argon, krypton and xenon have been studied. It is shown that the observed Lorentz shape of the bands results from two processes: vibrational dephasing and rotational diffusion. In contrast to fundamental transitions A1g - F1u, for the (v 2 + v 3) state it has proved necessary to apply two limiting cases: when the anharmonic level splitting ΔE anh is much greater than the Coriolis coupling, and when ΔE anh is small relative to the Coriolis coupling. Measured values of band halfwidths are compared with the theoretical values, obtained with the help of a rotational diffusion model. It is concluded that, in contrast to SF6, vibrational dephasing and intermolecular interactions contribute essentially to the formation of band contours of heavy metal hexafluorides. The second moment for the (v 2 + v 3) band has been estimated. The characteristic times of angular momentum correlation for SF6, UF6, MoF6 and WF6 molecules i...