Gaugeinvariant expectation values of the energy of a molecule in an electromagnetic field
In this paper, we show that the full Hamiltonian for a molecule in an electromagnetic field can be separated into a molecular Hamiltonian and a field Hamiltonian, both with gaugeinvariant expectation values. The expectation value of the molecular Hamiltonian gives physically meaningful results for the energy of a molecule in a timedependent applied field. In contrast, the usual partitioning of the full Hamiltonian into molecular and field terms introduces an arbitrary gaugedependent potential into the molecular Hamiltonian and leaves a gaugedependent form of the Hamiltonian for the field. With the usual partitioning of the Hamiltonian, this same problem of gauge dependence arises even in the absence of an applied field, as we show explicitly by considering a gauge transformation from zero applied field and zero external potentials to zero applied field, but nonzero external vector and scalar potentials. We resolve this problem and also remove the gauge dependence from the Hamiltonian for a molecule in a nonzero applied field and from the field Hamiltonian, by repartitioning the full Hamiltonian. It is possible to remove the gauge dependence because the interaction of the molecular charges with the gauge potential cancels identically with a gaugedependent term in the usual form of themore »
 Authors:

;
^{[1]}
 Department of Chemistry, Michigan State University, East Lansing, Michigan 48824 (United States)
 Publication Date:
 OSTI Identifier:
 22493682
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Chemical Physics; Journal Volume: 144; Journal Issue: 4; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 74 ATOMIC AND MOLECULAR PHYSICS; CHARGED PARTICLES; COORDINATES; ELECTROMAGNETIC FIELDS; EXPECTATION VALUE; GAUGE INVARIANCE; HAMILTONIANS; LAGRANGIAN FUNCTION; MOLECULES; POTENTIALS; QUANTUM MECHANICS; SCALARS; TIME DEPENDENCE; VECTORS