Optical spectra of trivalent lanthanides in LiYF4 crystal

Systematic calculations of multiplet energy levels of all trivalent lanthanides in LiYF4 (YLF) crystal were performed using two completely different approaches: diagonalization of the commonly used semi-empirical Hamiltonian and a fully relativistic discrete-variational multi-electron (DV-ME) method which is based on a first-principles configuration-interaction (CI) calculation program using molecular spinors obtained by the discrete-variational Dirac–Slater (DV-DS) calculations. The energy level diagrams within 4fn electron configurations were obtained by the former method, while those including both 4fn and 4fn−15d1 configurations were obtained by the latter. Using the explicit many-electron wave functions, the absorption spectra of Pr3+, Ho3+, and Tm3+ in YLF were calculated and compared with the experimental data.