Energy distributions in multiple photon absorption experiments

Photofragmentation experiments on clusters and molecules are discussed. It is found that they involve multiple photon absorption. The distributions of the absorbed number of photons are approximated by Poisson distributions. The distribution of absorbed energy for various laser and molecular-beam parameters is also calculated. The spatially averaged distributions have a power-law behavior for low energy with a cutoff at an energy which is proportional to fluence, for a Gaussian laser beam.