Optical Transitions and Enhanced Angular Overlap Model for the Low Symmetry Europium(III) System

Abstract

Absorption, emission, and excitation spectra covering a wide energy range of 3000-58000 cm -1 for the Eu 3+ ion in the low symmetry system K 5 Li 2 EuF 10 have been reported. The emission spectra have been analyzed by taking into account the influence of the temperature onto the luminescence from the 5 D 0,1,2 multiplets. The observed energy intervals in transition bands characteristic for the europium ion have been assigned and modeled using a multistep approach developed for this system. A risk of producing numerical artifacts in the multidimensional parameter space has been minimized by its strong reduction based on the enhanced angular overlap model and standardization of the low symmetry crystal field. The reported results are satisfactory (the final rms error of the fitting below 9.2 cm -1 ), consistent in each step of the procedure and in line with the microscopic physicochemical picture of the crystal field effective interaction.

Synthesis and luminescence properties of novel Sr3Gd(PO4)3:Dy3+ phosphor

“…Generally speaking, the optical properties of the phosphors are often influenced by the structure of the host matrix, when Dy 3 þ is located at a high symmetry site (with an inversion center), the blue emission is dominant, whereas the yellow emission is stronger when Dy 3 þ is located at a low symmetry site (without an inversion center) [17,18]. The observed emission spectrum in this work suggests that the blue emission at 483 nm is stronger than the yellow emission at 575 nm, which means that Dy 3 þ is located at high symmetry sites in Sr 3 Gd(PO 4 ) 3 host, in accordance with crystal structure, which does not disobey that based on local symmetry of lanthanide it is impossible to determine the intensity of hypersensitive transitions [19].…”

Interpretation of europium(III) spectra

“…As a consequence of the high density of energy levels, the wave functions of these energy levels contain contributions of many 2S+1 L levels and it is very difficult to unambiguously assign a 2S+1 L J label to these levels. Only a small number of papers discuss these high-energy levels [112,115,118,213,264,306,492,493,[513][514][515][516]. A marked difference between charge-transfer bands and broad f-d transitions is the absence of a distinct splitting of the charge-transfer bands [526].…”

On standardization of low symmetry crystal fields

“…Ref. [21]). However, one first has to choose 24 parameters from 27 and second, indicate one from several different sets of the 24 parameters which represent given crystal field energy levels sequence.…”

“…Instead of promoting the S 1 set, V2S requires B 20 ′ to be the absolute maximum as the function of α and β [30,31] and RB 22 ″ positive by rotation about /2 γ π = if necessary [21]. Note that RBS and V2S give the same standardized set of parameters if B 20 is positive.…”