Effect of amplified spontaneous emission on selectivity of laser photoionisation of the 177Lu radioisotope

A significant deselecting effect of amplified spontaneous emission has been observed in the experiments on selective laser photoionisation of the ¹⁷⁷Lu radioisotope according to the scheme 5d6s^{2 2}D_3/2 → 5d6s6p ⁴F^o_5/2 (18505 cm^-1) → 5d6s7s ⁴D_3/2(37194 cm^-1) → autoionisation state (53375 cm^-1). The effect is conditioned by involvement of non-target isotopes from the lower metastable level 5d6s^{2 2}D_5/2(1994 cm^-1) into the ionisation process. Spectral filtering of spontaneous emission has allowed us to significantly increase the selectivity of the photoionisation process of the radioisotope and to attain a selectivity value of 10⁵ when using saturating light intensities.