Theoretical investigations of the optical spectra and EPR parameters for the isolated and pairs of trivalent ytterbium ions in Li6Y(BO3)3 crystal

Abstract The optical spectra and electron paramagnetic resonance (EPR) parameters ( g factors and hyperfine structure constants A ) for an isolated Yb 3+ ion in Li 6 Y(BO 3 ) 3 (LYB) crystal are investigated first by the complete diagonalization method based on the superposition model. The obtained results are in reasonable agreement with the experimental ones. For a pair of coupled Yb 3+ ions in crystals, the extensively used formulas to calculate EPR splitting lines for such pair cannot be directly adopted in the present study and thus we extend them to the case of arbitrarily directed vector R connecting the two Yb 3+ ions in crystal. By these amended formulas, we find that in addition to the interacting Yb 3+ pair with nearest distance R (=0.385 nm), the Yb 3+ pair with next-nearest distance R (=0.662 nm) would also make contribution to experimental EPR spectra. This point which was not noticed in previous works would help us further understand the energy transfer scheme between two Yb 3+ ions in crystals.