A model to describe molecular fragmentation into several fragments is prese
nted. The case where dissociation is induced by the absorption of a single
or several photons from ultrashort pulses is considered. Time-dependent per
turbation theory is employed to describe the excitation process and the sub
sequent fragmentation dynamics is treated using various theories treating d
irect and indirect break-up processes. The multiple fragmentation of the Fe
(CO)(5) molecule serves as a numerical example. Different experiments are s
imulated and, regarding the simplicity of the model, an overall excellent a
greement between theory and experiment is found, thus providing an insight
into the excitation and fragmentation dynamics under various conditions. (C
) 2001 American Institute of Physics.