Calculation of 4f~65d energy levels of Eu~(2+) ion in KX(X=Cl,Br,I) crystals

According to the coupling model of 4f6(7FJ) and 5d , a calculating method for 4f65d energy levels of Eu2+ion in KX(X = Cl,Br, I) crystals was proposed. The parameter expressions of energy levels were obtained and the numerical calculations were carried out. The calculated results agree with the exprimental values.