Multiphoton ionization of H- at 160 nm: A study on the production of protons

A study on the production of protons in multiphoton ionization of H- at 160 nm is presented. Two sequential channels requiring three photons are shown to compete, while a direct path requiring two photons is found to dominate over the sequential contributions. Results are presented for the electron spectrum and for the total proton yield. The electron spectrum shows in wel l-separated regions the contributions of each path leading to proton produc tion, while for the total proton yield, as a function of peak intensity the se contributions give a change in the slope of the curve. The relevance of this study is marked by the current availability of high-order harmonic gen eration sources, operating at similar wavelengths, pulse durations and inte nsities to those considered in the present work.