Evaluation of the collisionless contribution to the measured infrared multiphoton decomposition

Some of the problems associated with modelling infrared multiphoton decomposition of gaseous molecules are presented. As an example, the cumulative log normal distribution function model is presented in an experimental context where the effects of laser beam geometry and molecular collisions have been taken into account. It is argued that any laser radial profile other than Gaussian, including tophat, can unnecessarily complicate the testing of a model and should be used with caution.