Isotope shift in the spectrum of multiquantum absorption of nitromethane molecule in intense IR fields

The effect of isotope shift has been revealed in the spectra of absorption and dissociation of polyatomic molecules in an intense IR field, with no isotope shift present in the spectrum of linear absorption of a vibration being excited. The effect has been applied to separation of nitrogen isotopes in the nitromethane molecule. The effect considered increases considerably the number of molecules suitable for isotope separation by IR laser radiation. (Auth.)