4f(9)5d -> 4f(10) spin-allowed and spin-forbidden transitions of Ho3+ ionsin LiYF4 single crystals in the vacuum ultraviolet

The laser-induced fluorescence spectrum (LIF) of LiYF4:Ho3+ 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 th e spectrum. The transitions originated from the levels and the edge of the 4f(9)5d electronic configuration and they were assigned to the 4f(9)5d--> 4 f(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 I-5(8) of the 4f(10) electronic configuration and the Stark components of the levels of the 4f(9)5d electronic configuration in the spectral range fr om 120 to 158 nm and four main spin-forbidden transitions in the spectral r ange between 158 and 170 nm. Intraconfigurational 4f(10) --> 4f(10) dipole- forbidden transitions were observed as well in the VUV region of the spectr um from 170 to 190 nm. Finally, from the absorption spectrum the position o f the ground level I-5(8) of the 4f(10) electronic configuration was found to be 4200 +/- 800 cm(-1) above the top of the valance band of the LiYF4 cr ystal host. (C) 1999 Elsevier Science B.V. All rights reserved.