Angular dependence of isotope enrichment in ultrafast laser ablation plumes

Summary form only given. It has been observed that isotopic enrichment of light ions occurs in the central portion of laser ablation plumes when such plasmas are formed with ultrafast laser pulses. It was found that the separation of lighter isotopes from heavier isotopes occurs on axis in the expanding plasma plume. The relative independence of the enrichment on axis among different elements and other similarities in the ion distributions have indicated a universality to this effect that lends credence to a possible plasma centrifuge model. In the present work, we examine the angular distribution of isotope enrichments and investigate the dependence on laser parameters and on the atomic-transport mean free path between collisions. The angular dependence is studied as a function of ion energy, ion charge state, and atomic mass.