Phase coherence and collision models in radiatively driven oscillators

We consider the effects on the energy absorbed and the distribution of energy resulting from a phased response of a molecule to a driving laser field. Contrasting a Landau–Teller collision model with a strong collision model we compare the dynamic and steady-state solutions to our generalized master equation with solutions to an ordinary master equation, for truncated (finite-level) and nontruncated (infinite-level) harmonic oscillators. We find significant coherent enhancement in upper energy level populations which is most pronounced when an intense but below saturation laser field is present; these coherent effects, predicted for truncated oscillator level populations, are contrasted with the infinite level cases. We show that at steady state an ordinary master equation predicts the average energy of the harmonic oscillator correctly but fails to predict the correct population distribution of energy states.