Energy levels and interaction between Eu3+-ions at lattice sites of symmetryC 2 and symmetryC 3i in Y2O3

Abstract

Besides the known energy levels of Eu a+ at lattice sites of symmetry C z in YzO3, some transitions of this ion at lattice sites of symmetry Ca i in the same host crystal have been found and it was possible to construct the energy level scheme in part. Evidence for an energy transfer fl'om Eu 3+ (C 3 i) to Eu 3+ (C z) is given, the strength of which is rneasured as a function of the Eu203 concentration. The results lead to the assumption of a fixed distance R 0 for the interaction responsible for the energy transfer. A temperature-independent value of R0=8.7 ~ was found. The full explanation of the underlying quantum mechanical mechanism requires further experiments.

Excitation of Magnetic Dipole Transitions at Optical Frequencies

“…For details of this estimate, see the Supplemental Material [30]. We emphasize that while spontaneous MD emission from rare earth ions has been shown before [1,[7][8][9][10], our work unambiguously demonstrates the selective excitation of a MD transition. Since excitation is a stimulated process, similar measurement techniques can be employed for demonstrating stimulated transitions from the excited state and achieving lasing through magnetic dipole transitions.…”

“…Nature, however, also provides materials with strong MD transitions, namely, rare earth ions. Many of their MD transitions are found within the visible spectrum, making them promising candidates for the optical excitation of MD transitions.Much theoretical and experimental work has been done exploring the MD and ED contributions to spontaneous emission from Eu 3þ and other trivalent rare earth ions [1,[7][8][9][10]. Lifetimes and oscillator strengths have been studied as a function of local environment [11][12][13][14], ion concentration [15][16][17], and particle size [18][19][20][21][22][23].…”

Cathodoluminescence of Nanocrystalline Y2O3:Eu3+with Various Eu3+Concentrations

“…[13][14][15][16][17][18][19] In the earlier studies [4][5][6][7][8][9][10][11][12] the focus was on the interpretation of the excitation and emission spectra in terms of energy transfer in the Y 2 O 3 :Eu 3+ crystals, whereas in the latter studies [13][14][15][16][17][18][19] the attention shifted toward the synthesis of nanomaterials. Most studies used photoluminescence (PL) techniques, [4][5][6][7] which enabled the excitation of energy levels having a particular symmetry and yielded insight on the energy flow in Y 2 were limited to the evaluation of the luminous efficiency. [10][11][12] A detailed investigation of the energy flow in Y 2 O 3 :Eu 3+ after excitation by an electron beam was performed by Klaassen et al 8 These authors also studied saturation effects in Y 2 O 3 :Eu 3+ at high current densities in an electron microscope.…”

“…This selection is not trivial, because many peaks in the spectrum of Y 2 O 3 :Eu 3+ suffer from overlap or are combinations of more than one spectral transition. 5,6 The first phase in the energy flow in Y 2 4,20 In Y 2 O 3 there are two different Y 3+ lattice sites, which possess the point symmetries C 2 and S 6 (Schoenflies notation): 24 lattice sites have C 2 symmetry, while the other 8 have S 6 symmetry. Both sites are six coordinate and are thus present in the ratio of 3:1.…”

“…Before 1996 these studies were focused mainly on micrometer sized particles, [4][5][6][7][8][9][10][11][12] more recently the attention has been directed to nano-sized powder materials. [13][14][15][16][17][18][19] In the earlier studies [4][5][6][7][8][9][10][11][12] the focus was on the interpretation of the excitation and emission spectra in terms of energy transfer in the Y 2 O 3 :Eu 3+ crystals, whereas in the latter studies [13][14][15][16][17][18][19] the attention shifted toward the synthesis of nanomaterials. Most studies used photoluminescence (PL) techniques, [4][5][6][7] which enabled the excitation of energy levels having a particular symmetry and yielded insight on the energy flow in Y 2 were limited to the evaluation of the luminous efficiency.…”