A. J. Salkeld, M. F. Reid, J-P. R. Wells, G. Sánchez-Sanz, L. Seijo and Z. Barandiarán.
Effective-Hamiltonian parameters for ab initio energy-level calculations of SrCl2 :Yb2+ and CsCaBr3:Yb2+.
Calculated energy levels from recent ab initio studies of the electronic structure of SrCl2:Yb2+ and CsCaBr3:Yb2+ are fitted with a semi-empirical 'crystal-field' Hamiltonian, which acts within the model space 4f14 + 4f135d + 4f136s. Parameters are obtained for the minima of the potential energy curves for each energy level and also for a range of anion–cation separations. The parameters are compared with published parameters fitted to experimental data and to atomic calculations. The states with significant 4f136s character give a good approximation to the impurity-trapped exciton states that appear in the ab initio calculations.