Molecular quantum electrodynamics

Abstract A comparison is made of the conventional quantum mechanical hamiltonian for the interaction of molecular systems with the electromagnetic field and the alternative multipole formulation given recently (Atkins & Woolley 1970). The conventional hamiltonian is first derived by using Dirac’s generalized hamiltonian theory in which the Coulomb gauge condition is introduced as a supplementary condition. We analyse further the interpretation of the unitary transformation that connects the two hamiltonians in terms of the arbitrariness of the phase of the wavefunctions of charged particles in the presence of the electromagnetic field, and finally examine the problem of exhibiting explicitly the binding energies of the molecular systems.