Electronic spectra of Pr3+ doped mixed alkali borate glasses

An investigation of the optical absorption spectra of 1 mol% Pr2O3 in mixed alkali borate glasses of the type xNa(2)O. (30-x) K(2)0.69B(2)O(3).1Pr(2)O(3) (x=5,10,15, 20 and 25) is presented. The glasses were obtained by quenching melts consisting of Na2CO3, K2CO3, H3BO3 and Pr2O3 (850-1000degreesC, 1(.)5-2 h) between brass plates. Spectroscopic parameters like Racah (E-1, E-2 and E-3) and spin orbit (xi(4f)) interaction parameters and Judd-Ofelt intensity parameters (Omega(2), Omega(4) and Omega(6)) have been calculated as a function of x in the glass matrix. Radiative and nonradiative transition rates (A(T) and W-MPR), radiative lifetimes (tau(R)), branching ratios (beta) and integrated absorption cross sections (Sigma) are reported for certain excited states of Pt3+ in all glasses studied. Variations of these parameters as a function of composition are discusscd in terms of covalency and of changes into the crystal field around the Pr3+ ions caused by structural changes of the glass matrix.