Study of Spectroscopic Properties of Diatomic Molecules Based on High Orders of the Operator Perturbation Theory

The form of the effective Hamiltonian of a quantum system with allowance for corrections of arbitrary order for solving arbitrary quantum-mechanical problems with perturbation operator depending not only on the same coordinates as the operator of the zero approximation, but also on an arbitrary set of other coordinates whose derivative operators may not commute with each other, is retrieved based on the operator perturbation theory (the recurrence formulas for corrections of any arbitrary order of the operator perturbation theory are presented in the paper in the most general form). The general results obtained allow the special features of the effective operators of any polyatomic molecule to be investigated. As a first step, an arbitrary diatomic molecule is investigated. Isotopic relations among different spectroscopic parameters are derived for the parent molecule and its various isotopic modifications.