Nonlinear response of a harmonic diatomic molecule: Algebraic nonperturbative calculation

Even harmonic molecules display a nonlinear behavior when driven by an inhomogeneous field. We calculate the response of single harmonic molecules to a monochromatic time and space dependent electric field E(r,t) of frequency ω employing exact algebraic methods. We evaluate the responses at the fundamental frequency ω and at successive harmonics 2ω, 3ω, etc., as a function of the intensity and of the frequency of the field and compare the results with those of first and second order perturbation theory