STATISTICAL ASPECTS OF THE RADIATIVE EXCITATION OF THE HARMONIC-OSCILLATOR

We report solutions of the master equation for infrared multiphoton ex citation of a harmonic oscillator with linear dipole function in a the rmal radiation field (including spontaneous emission). The time-depend ent populations and wave packet motions are discussed in comparison to coherent laser excitation and in relation to quantum ''chaotic'' moti on arising from random phases in a perfectly regular spectrum. A Loren tzian envelope for high overtone line strength distributions arising f rom hypothetical highly nonlinear dipole functions of the harmonic osc illator allows one to reconstruct a Bixon-Jortner-like model with a si mple one-dimensional harmonic oscillator. Numerical simulation of cohe rent radiative resonance overtone excitation shows Rabi oscillation co rresponding to an effective two-level model. Short-pulse excitation pr epares a superposition state which thereafter decays. This decay corre sponds to a simple one-dimensional motion of an initially displaced wa ve packet, with the expected recurrence at the oscillator period, but without substantial intermediate spreading of probability.