Space charge effects in the ion time-of-flight spectra following non-resonant multiphoton ionization

The authors present a kinetic model which describes the evolution of charged particles produced by high-intensity, ultrashort laser pulses, in non-resonant multiphoton ionization (MPI) processes. The model is based on the Vlasov-Maxwell equation and on the approximation of a linear profile for the space charge field. It has been used for predicting waveforms of the ion detector signal obtained in non-resonant MPI of Xe atoms with 30 ps, 1013 W cm-2, 1.064 mu m laser pulses. The comparison of computed and experimental results is satisfactory, thus underlying the relevance space charge effects in typical non-resonant MPI conditions, and showing the effectiveness of the model in accounting for them.