An empirical model is given, which allows a satisfactory description of essential residts of the collisionless mulliphoton dissociation of uranyl compounds by means of an IR laser (e.g. absorption cross section, fluence and frequency dependence of the yield and its isotope effect) with a small mathematical effort. Especially it is possible to explain theoretically the origin of the observed isotope effect and to describe the absorption of laser energy and its redistribution within the other vibrational modes of the molecule.