Description of muitiphoton collisioniess dissociation of isotopes of the SF6 molecule

A solution is obtained for the evolution operator of a multilevel system interacting with a monochromatic field containing no secular terms. This is used to describe the initial stage of excitation of the ν₃ mode of the SF₆ molecule. Excitation in the quasicontinuum band is described by the diffusion equation. An equation is derived for the probability of dissociation of isotopes of the SF₆ molecule as a function of the field parameters and the temperature. The experimental results are accurately approximated by this equation. The possibility of isotopically selective excitation of heavy molecules having a small isotope shift in a field of 10¹⁰ W/cm² intensity is discussed.