Laser isotope separation of lithium by two-step photoionization

Abstract

Lithium isotope separation has been achieved employing the two-step photoionization technique along with a narrow band dye laser in conjunction with a time of flight mass spectrometer. The demonstrated method yields a high degree of selectivity by tuning the dye laser at the resonance levels of Li6 and Li7. It is inferred that the concentration of the natural abundance of the Li6 isotope gets enhanced up to over 47% as the exciter dye laser is tuned to the P1∕22 of Li6 even if the linewidth of the exciter laser is not sufficiently narrow to excite the isotopic level. It is also noticed that the much higher energy density of the exciter laser limits the resolution of the fine structure levels of the lithium isotopes that leads to a loss in the enrichment of Li6 due to the power-broadening effect. Measurements of the photoionization cross section of the lithium isotopes from the 2pP1∕2,3∕22, excited states for Li6 and Li7 and the corresponding number densities are reported.