The Born-Oppenheimer method for normal molecules

Abstract

The Born-Oppenheimer method for a normal molecule is considered, the body-fixed moving-coordinate system being defined by means of the Eckart conditions. A new method of transformation of the Hamiltonian to the set of body-fixed coordinates is proposed. The equations of electronic, vibrational, rotational and translational motion are derived in explicit form. The zeroth and the first terms are calculated in the eigenfunction expansion and the eigenvalue expansion is calculated up to the fifth term.