Ion desorption induced by ultraviolet laser radiation pulses was studied in surfaces in vacuum. The ion desorption from three different solids was analyzed: insulin, carbon (amorphous and graphite) and polycrystals of alkali halides. The main processes involved in the laser-solid and laser-vapor interactions, as well as in the plasma evolution, were well described by a thermal model and by the simulation of the time-of-flight spectra for the first moments of the plasma expansion to vacuum. A new method to determine the initial velocity and the beginning of the free expansion regime as a function of the laser intensity was proposed for LDI (Laser Desorption Ionization) and MALDI (Matrix Assisted Laser Desorption Ionization). Considering the complexity of the dynamical treatment of the expansion of the laser-generated plasma, an analysis by using several combinations of irradiated solids was performed. It was established that the desorption process is characterized by two main mechanisms: i) the atomization followed by recombination of the target elements in clusters and ii) the emission of preformed clusters of the target material. The most stable geometric structures of the measured species were characterized using Density Functional Theory (DFT) and classified taxonomically as a function of their internal total energy (D-plot method); the influence of the structure`s stability on the relative mass abundances was also determined.