A simple model for multiphoton molecular absorption

Abstract

A simple model is provided for the multiphoton absorption process in a gas based on the discrete level, quasicontinuum picture. The model is an extension of one used to describe saturation of a laser medium. Numerical solutions for the fractional energy absorbed illustrate a number of features observed in experiments. These include a wide range of behavior for the fractional energy absorbed vs fluence, including a positive slope. A second feature is the relatively large value for the fractional energy absorbed, even when the ground-state cross section is small.