Estimates of the A²-term in the interaction of matter with radiation

If the energy of a molecule coupled to the quantised radiation field is made an extremum with respect to products of arbitrary molecular states and coherent field states, then there results a nonlinear Schrodinger equation for the molecule from which bounds for the energy contribution of the A 2 -term are derived. It is shown in what sense this contribution can be expected to be small under rather general circumstances.