Energy levels of Pr³⁺:GdOCl under pressure

Abstract

Excitation and luminescence spectra of Pr 3+ in GdOCl were measured in the spectral range from 11 000 cm −1 to 22 500 cm −1 . At ambient pressure a total of 54 spectral lines were observed. Some of these lines cannot be explained by transitions between crystal-field levels of the regular Pr 3+ site in GdOCl. Possible explanations of these lines are discussed. Under pressure up to 16 GPa, all lines exhibit a red-shift, from which a part of the energy level scheme of the 4f 2 configuration could be derived. From the 34 levels at ambient pressure, 31 could also be obtained under pressure. The energy level scheme is described in terms of the free-ion parameters (F k , α, β, γ , ζ , M k , P k ) and crystal-field parameters (B 2 0 , B 4 0 , B 4 4 , B 6 0 , B 6 6 ). The variations of these parameters under pressure were determined. Surprisingly, the crystal-field strength, calculated from the crystal-field parameters, first shows a slight decrease with increasing pressure.

Nephelauxetic Effects in the Electronic Spectra of Pr3+

“…It was discovered from the pressure-dependence of the optical spectra of Pr 3+ that both F k and ζ 4f decrease with increasing pressure. 15 The decreases of Slater parameters follow the order ΔF 2 /F 2 > ΔF 4 /F 4 > ΔF 6 /F 6 , and the relative decrease Δζ 4f /ζ 4f is smaller than that of F 2 , but similar to those of F 4 and F 6 . Holzapfel's group 15,16 employed a combination of the Central Field Model and the Symmetry-Restricted Covalency Model to attempt to explain the results for ROCl:Pr 3+ (R = Pr, La, Gd) and LaCl 3 :Pr 3+ under pressure.…”

“…15 The decreases of Slater parameters follow the order ΔF 2 /F 2 > ΔF 4 /F 4 > ΔF 6 /F 6 , and the relative decrease Δζ 4f /ζ 4f is smaller than that of F 2 , but similar to those of F 4 and F 6 . Holzapfel's group 15,16 employed a combination of the Central Field Model and the Symmetry-Restricted Covalency Model to attempt to explain the results for ROCl:Pr 3+ (R = Pr, La, Gd) and LaCl 3 :Pr 3+ under pressure. The Central Field Model envisages that F k and ζ 4f decrease from the gas to the condensed phase due to an isotropic expansion of the 4f orbitals.…”

Effect of pressure on free-ion and crystal-field parameters ofPr3+inLOCl(L=Bungenstock1, Tröster2, Holzapfel3 2000Phys. Rev. B362181View full textAdd to dashboardCite

“…It has been shown that the spectra of PrGd at ambient pressure corresponded to high-pressure spectra of PrLa. 5 Comparing the spectra of PrPr with PrLa it is found that the ambient pressure spectra of PrPr also correspond to the high-pressure spectra of PrLa, but at a much smaller pressure than in the case of PrGd. This series, PrLa → pressure PrPr → pressure PrGd, is also observable when the behavior of the unknown lines is studied.…”

“…This is in agreement also with results for PrGd. 5 In connection with this observation, an interesting point concerns the comparison of the ground level of all three samples. For PrGd the ground level is 3 H 4 (E) and the first excited level 3 H 4 (A 1 ).…”

“…4,5 The spectra of both samples were very similar, including the appearance of new lines under pressure that could not be assigned unambiguously. In this paper, the investigations were extended to PrPr mainly to verify whether the spectra show similar features, while local distortions, present in the other samples, can be excluded.…”