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.