Selective photoionisation of lutetium isotopes

A three-stage laser photoionisation scheme intended for enriching the ¹⁷⁶Lu isotope from natural lutetium was considered. An investigation was made of the hyperfine structure of the second excited state 5d 6s 7s → ⁴D_3/2 with an energy of 37 194 cm^-1 and the autoionisation state with an energy of 53 375 cm^-1 of the ¹⁷⁶Lu and ¹⁷⁵Lu isotopes. The total electron momentum of the autoionisation level and the constant A of hyperfine magnetic interaction were determined. Due to a small value of the isotopic shift between ¹⁷⁶Lu and ¹⁷⁵Lu, appreciable selectivity of their separation may be achieved with individual hyperfine structure components. The first tentative enrichment of the 176Lu isotope was performed to a concentration of 60 % — 70 %.