The efficiency of the nonlinear mechanism of changing the Н2О intermolecular interaction potential due to radiative excitation of rotational-vibrational transitions is studied. It is shown that the corresponding short-term changes of the virial coefficients in the equation of state of a nonideal gas can provide for transition of the atmospheric seed nuclei through the forbidden size zone to the zone of condensation-active droplets thus initiating the high-energy macroprocess of removing excess supersaturation in a medium at phase transition.