The 1S level of Pr3+ in LaCl3

Abstract
The 1S0 level of Pr3+:LaC13 has been located in the wavelength region inaccessible to the single‐photon absorption method. It was observed at 46 450.6±5 cm1 by using the two‐photon absorption technique. All 13 levels of the 4f2 configuration are now known with high precision and a new parametric fit of the ground configuration levels is presented. Since the reported position of this level in the free ion is doubtful, a suggestion is made on finding the correct value.