Optical spectroscopy of Pr3+ in KGd(WO4)(2) single crystals

The polarized optical absorption (OA) and photoluminescence of Pr3+ doped K Gd(WO4)(2) (KGW) single crystals have been measured at selected temperature s between 7 and 300 K. For the studied Pr concentrations, [Pr] = 0.03 x 10( 20)-1.9 x 10(20) cm(-3) a unique site is observed. 74 energy levels were ex perimentally determined for this site and labelled with the appropriate A o r B irreducible representations corresponding to the C-2 symmetry of the Gd point site in KGW. The set was fitted to a Hamiltonian of adjustable param eters including free-ion as well as real B-q(k) and complex S-q(k) crystal- field parameters A good simulation of the experimental crystal field energi es was achieved with a root mean square deviation sigma = 15.3 cm(-1). Dist ortions in the oxygen bonds to Pr3+ are found to contribute to the broadeni ng of some OA bands, particularly those related to the D-1(2) multiplet. Th e OA edge is determined by the interconfigurational 4f--> 4f(1)5d(1) Pr3+ t ransition peaking at 34 200 cm(-1). From the average 300 K OA cross section s the radiative lifetimes of the Pr3+ multiplets have been calculated consi dering the standard and modified Judd-Ofelt (JO) theories. A better agreeme nt with the experimental results is obtained by the standard theory: the av erage JO parameters obtained at <(<Omega>)over bar>(2) = 12.0 x 10(-20) cm( 2), <(<Omega>)over bar>(4) = 8.15 x 10(-20) cm(2) and <(<Omega>)over bar>(6 ) = 2.64 x 10(-20) cm(2). Electrons excited to the P-3(0) multiplet decay v ery efficiently to the D-1(2) multiplet even at 15 K. In samples with [Pr] greater than or equal to 0.3 x 10(20) cm(-3) the excitation of the D-1(2) m ultiplet decays non-radiatively by an electric dipole-dipole transfer betwe en Pr neighbours.