The operator method for perturbations in the theory of infrared molecular spectra

Abstract

The principles for constructing effective Hamiltonians applicable to molecular spectroscopy are considered. The degree of indeterminacy of a fully effective Hamiltonian is investigated and of a Hamiltonian effective in a subspace. A modification of contact transformations is formulated using the Primas technique of superoperators. Explicit expressions are also given for corrections to effective Hamiltonians of the contact-transformations method up to the sixth order of a small parameter.