LETTER TO THE EDITOR: S-matrix analysis of ionization yields of noble gas atoms at the focus of Ti:sapphire laser pulses
We analyse the experimental data for the formation of different charge states of a whole sequence of noble gas atoms in the presence of intense femtosecond Ti:sapphire laser pulses, using a recently developed dynamical model of laser-induced n-fold ionization of a complex atom. The ion yields for single and double ionization, as well as their ratios, are calculated for He, Ne, Ar, Kr and Xe and are found to agree remarkably well with the corresponding experimental data (with the possible exception of Ne). Next, we compare the experimental ion yields for the triple ionization of Ar with the present theoretical results which also show excellent agreement over the entire intensity range and reproduce the measured knee structures. Our analysis indicates that direct escapes of up to three electrons can contribute significantly to the ion yields for the highest charge state of Ar (namely, Ar3+) observed so far. Finally, for the purpose of future experimental references, we present the predicted results for the yields of up to sixfold ionization from neutral Ar or Ar+ ion.