Simulation of the crystal field effect on the Pr~(3+) ion in K_2La_(1-x)Pr_xCl_5 ternary chlorides

摘要

The high resolution absorption, luminescence and excitation spectra of the orthorhombic potassium lanthanum praseodymium ternary chloride, K_2La_(1-x)Pr_xCl_5 (0.02 < = x < = 0.15) single crystals were recorded at 4,77 and 293 K with different excitation sources. The experimental 4f~2 energy level scheme of the Pr~(3+) ion in K_2LaCl_5 derived from the absorption and emission spectra consisted of 86 (out of 91) Stark components. This energy level scheme was simulated by using a phenomenological crystal field (cf) model which included eight free ion and nine cf parameters according to the C_(2v) symmetry. Despite the approximate C_(2v) point symmetry instead of the real C_s one, the simulation yielded a very satisfactory rms deviation of 17cm~(-1) between the experimental and calculated energy level schemes. The results, especially the weak cf strength, are discussed taking into account the bonding characteristics in K_2LaCl_5.