Observation and simulation of the energy-level scheme of the Pr3+ion in REOCI

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Abstract
Absorption spectra of REOCI (RE = La, Pr, Gd and Y) have been measured in the range 435–950 nm at ambient, liquid nitrogen and liquid helium temperatures. Luminescence from the 3P1, 3P0 and 1D2 levels in PrOCI, LaOCI/Pr3+, GdOCI/Pr3+ and YOCI/Pr3+(Pr3+ content 2 mol%) was observed under argon-ion laser excitation in the visible region between 475 and 800 nm. The transitions were assigned and the energy-level scheme derived from absorption and emission spectra and consisted of some 50 levels; i.e. 68 Stark components out of 91 for the 4f2 configuration. This set was fitted to a Hamiltonian of 13 adjustable parameters including free-ion [Racah's (E0–3), Tree's (α, β and γ) and spin—orbit coupling constant (ζ) as well as crystal-field (B2 0, B4 0, B4 4, B6 0 and B6 4) parameters. Good simulation of the experimental energy-level scheme was achieved with a root mean square deviation equal to 17 cm–1. A comparison with the energy-level parametrization of Nd3+(4f3) in NdOCl, as well as of Eu3+(4f6) and Tb3+(4f8) in GdOCl, shows the consistency of the present results.