Vacuum ultraviolet spectroscopy of Ce(3+)-doped SrMgF(4) with superlattice structure.
JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2006;
18:6033-6044. [PMID:
21690816 DOI:
10.1088/0953-8984/18/26/021]
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Abstract
X-ray diffraction of Ce(3+)-doped SrMgF(4) (SMF:Ce) crystals shows a superlattice structure, reflecting the distribution of Ce(3+) polyhedra centres observed in optical experiments. Optical absorption bands and fluorescence bands from the Ce(3+) polyhedra centres overlap in the vacuum ultraviolet (VUV) and ultraviolet (UV) regions, respectively, so that wide pumping and tuning ranges are expected for laser operation. The SMF:Ce crystals, as well as the isomorphous BaMgF(4), are candidates for a tunable laser gain material with nonlinear properties. The optical absorption, excitation, and fluorescence bands observed in the SMF:Ce crystals at low temperatures are ascribed to five distinct fluorescent centres. Three centres have well-known Ce(3+) optical characters, for example, fluorescence with double peaks separated by 2000 cm(-1) and five resolved absorption/excitation bands. These centres are assigned to Ce(3+)-polyhedra classified by weak and strong crystal fields as a consequence of the superlattice structure. The other two fluorescence bands observed in the visible region have 1.5-2 times larger linewidths than those of the former three bands. These bands are interpreted as optical transitions from complexes consisting of Ce(3+) and one or two electrons trapped at a vacancy of the nearest neighbour F(-) ligand ions.
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