4f 95d→4f 10 spin-allowed and spin-forbidden transitions of Ho 3+ ions in LiYF 4 single crystals in the vacuum ultraviolet

Abstract

The laser-induced fluorescence spectrum (LIF) of LiYF 4:Ho 3+ single crystals, pumped by the molecular fluorine pulsed discharge laser at 157.6 nm, was obtained in the vacuum ultraviolet (VUV) and ultraviolet (UV) regions of the spectrum. The transitions originated from the levels and the edge of the 4f 95d electronic configuration and they were assigned to the 4f 95d→4f 10 interconfigurational spin-allowed and spin-forbidden transitions. The absorption spectrum of the crystal samples in the VUV was obtained as well. We observed five main dipole-allowed transitions between the ground level 5 I 8 of the 4f 10 electronic configuration and the Stark components of the levels of the 4f 95d electronic configuration in the spectral range from 120 to 158 nm and four main spin-forbidden transitions in the spectral range between 158 and 170 nm. Intraconfigurational 4f 10→4f 10 dipole-forbidden transitions were observed as well in the VUV region of the spectrum from 170 to 190 nm. Finally, from the absorption spectrum the position of the ground level 5 I 8 of the 4f 10 electronic configuration was found to be 4200±800 cm −1 above the top of the valance band of the LiYF 4 crystal host.