Experimental and theoretical investigations of the 4f(2) -> 4f5d ground-state and excited-state absorption spectra of Pr3+ in LiYF4

Near-UV excited-state absorption spectra obtained with a pulsed pump-probe technique were recorded in LiYF4:Pr3+ at 77 and at 8 K and revealed a detai led structure of the 4f(2 1)D(2) --> 4f5d and 4f(2) (P-3(0) + I-1(6)) --> 4 f5d optical transitions. These experimental results, together with those pr eviously obtained at room temperature, are compared with the numerical pred ictions of a full calculation of the 4f5d sublevels and of the electric dip ole transitions toward these sublevels from different states of the 4f2 con figuration. The agreement is good, provided that the four adjustable parame ters of the theory are taken as B-20(5d) = 7290 cm(-1), B-40(5d) = -14 900 cm(-1), F-0 = 60 557 cm(-1), and (r)(fd) = 0.245 Angstrom. The level struct ure of the 4f5d configuration of LiYF4:Pr3+ is shown to be dominated, as ex pected, by the crystal field coupling of the 5d electron but also, to a not iceable extent, by the spin-orbit coupling of the 4f electron and the Coulo mb repulsion of both electrons. The former of these two interactions is som ewhat more efficient than the latter in the low-energy part of the 4f5d con figuration, i.e., in the spectral region where the largest amount of experi mental data is currently available. (C) 2000 Optical Society of America [S0 740-3224(00)01407-7].