Velocity-dependent property surfaces and the theory of vibrational circular dichroism

Abstract

The familiar idea of a molecular property surface in which a property (such as the dipole moment) is expressed as a function of nuclear coordinates R I , is extended to cover properties odd under time-reversal by including the nuclear velocities ·R I as variables. One such property is the magnetic dipole moment m . This approach relates magnetic dipole vibrational transition moments to derivatives (∂ m / ∂ ·R I ) which may be calculated within the clamped-nucleus approximation, and used in the theory of vibrational circular dichroism. The same derivatives describe the electric field at a nucleus induced by an external dynamic magnetic field, leading to a physically transparent description of VCD. Sum rules relate these derivatives to the molecular paramagnetizability.