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Spectra, energy levels, and symmetry assignments for Stark components of Eu3+(4f6) in gadolinium gallium garnet (Gd3Ga5O12)

John B. Gruber, University of Texas at San Antonio
Uygun V. Valiev, National University of Uzbekistan
Gary W. Burdick, Andrews University
Sharof A. Rakhimov, National University of Uzbekistan
Madhab Pokhrel, University of Texas at San Antonio
Dhiraj K. Sardar, University of Texas at San Antonio

Abstract

Absorption and fluorescence spectra observed between 450 and 750 nm at 85 K and room temperature (300 K) are reported for Eu3+(4f6) in single-crystal Czochralski-grown garnet, Gd3Ga5O12 (GGG). The spectra represent transitions between the 2S+1LJ multiplets of the 4f6 electronic configuration of Eu3+ split by the crystal field of the garnet. In absorption, Eu3+ transitions are observed from the ground state, 7F0, and the first excited multiplet, 7F1, to multiplet manifolds 5D0, 5D1, and 5D2. The Stark splitting of the 7FJ multiplets (J=0–6) was determined by analyzing the fluorescence transitions from 5D0, 5D1, and 5D2 to 7FJ. The Eu3+ ions replace Gd3+ ions in sites of D2 symmetry in the lattice during crystal growth. Associated with each multiplet manifold are 2J+1 non-degenerate Stark levels characterized by one of four possible irreducible representations (irreps) assigned by an algorithm based on the selection rules for electric-dipole (ED) and magnetic-dipole (MD) transitions between Stark levels in D2 symmetry. The quasi-doublet in 5D1 was characterized by an analysis of the magnetooptical spectra obtained from the transitions observed between 5D1 and 7F1. A parameterized Hamiltonian defined to operate within the entire 4f6 electronic configuration of Eu3+ was used to model the experimental Stark levels and their irreps. The crystal-field parameters were determined through use of a Monte-Carlo method in which nine independent crystal-field parameters, Bkq, were given random starting values and optimized using standard least-squares fitting between calculated and experimental levels. The final fitting standard deviation between 57 calculated-to-experimental Stark levels is 5.9 cm-1. The choice of coordinate system, in which the nine Bkq are real and the crystal field z-axis is parallel to the [0 0 1] crystal axis and perpendicular to the xy plane, is identical to the choice we used previously in analyzing the spectra of Er3+ and Ho3+ garnets.

Suggested Citation

John B. Gruber, Uygun V. Valiev, Gary W. Burdick, Sharof A. Rakhimov, Madhab Pokhrel, and Dhiraj K. Sardar. "Spectra, energy levels, and symmetry assignments for Stark components of Eu3+(4f6) in gadolinium gallium garnet (Gd3Ga5O12)" Journal of Luminescence 131 (2011): 1945-1952.