EPR Investigations ofCe3+in Cubic Sites of CaO, SrO, and BaO

Abstract

3) the corrected values for the transition energies in keV. The uncertainties in the values of E th in Table II range from 5 to 10 eV, and are the same as in Dixit et al. We see now by a comparison of the theoretical and experimental values that the discrepancy is reduced considerably, the only transitions having any significant discrepancy being the 4f-3d transition in Ba and the 5^-4/transition in Pb.We have also considered the effect of the finite size of the nucleus on the vacuum-polarization corrections: The rather complicated convolution integral required to do this in configuration space becomes a trivial multiplicative factor in the momentum-space integral. Taking the uniform model for the nuclear shape, we find that the individual shifts are increased by rather less than 1%, giving less than 10 eV from the Uehling term itself, and correspondingly smaller corrections from the higher-order terms. A more realistic model for the nuclear shape can hardly be expected to give rise to any significant difference.An effect of the same magnitude arises if the vacuum-polarization potential is included in the Dirac equation itself, rather than treating it perturbatively as we have done. The E th in Table II is, in fact, calculated by the former method; the difference between this value and the perturbative value is of the order of 10 eV.A number of authors 5 * 6 have suggested a possible anamolous interaction of the muon via a scalar field. The model suggested by Bar shay, 5 with a scalar meson of mass around 750 MeV, turns out to give shifts of less than 1 eV for the states in which our interest lies; this is because the large mass implies a very short-range forceThe electron paramagnetic resonance (EPR) spectrum of Ce 3+ (4/ 1 configuration) in cubic single crystals has previously been the subject of numerous investigations. 1 " 6 Until the present which dominantly affects only the 5-wave states. We note that the 4/-3d transition in Ba and the 5^-4/transition in Pb have almost equal discrepancies of about 70 eV. This enables us to put a rather good upper limit on the mass m s of the scalar meson of about 8 MeV. Assuming this mass, the required coupling constant is G s = g silll X £SNN = 6 x 10 " 7 . The final column in Table II shows the theoretical value, including the effects of this particle, once again incorporating the effects of the finite nuclear size. It is remarkable that the remaining discrepancy is eliminated:The reader is at liberty to regard this as evidence for a physical particle of mass 8 MeV, coupling mainly to M"V". It is amusing to speculate that if this particle is very weakly coupled to e *e", it would escape experimentally detection, as well as provide a mechanism for the breaking of \ie universality. . work, however, no EPR spectra have been reported which could be attributed unequivocally to Ce 3+ in a cubic symmetry site. 7 The observation of the EPR spectrum of Ce 3+ in a site of local cu-The EPR of Ce 3+ has been observed in sites of cubic symmetry for the first time. The unusually large...

Crystal and magnetic structure of CeVO3

“…This is much smaller than gJ = 2.14 μ B , the theoretical moment of the Ce 3+ ion (electron configuration 4f 1 , J = 5/2). While the magnetic moments of many insulating Ce 3+ compounds (such as CeOBr, [25]) are in good agreement with the free-ion value, significant deviations have been observed in some oxides (such as Ce 3+ impurities in (Sr,Ca,Ba)O [26]). Possible origins include partial quenching of the orbital moment by the crystal field, covalency with ligand ions, and orbit-lattice interactions.…”

Spectroscopic properties of photorefractiveBaTiO3double doped with cerium and rhodium

“…A feature of the work of Reynolds et al 35 that is also relevant here is that they reported the EPR of Ce 3ϩ located at sites of cubic symmetry. The observed g factors were in the range of 0.79 to 0.93, depending on the host.…”

“…The discrepancy between the calculated and experimental g factors for Ce 3ϩ in various hosts has been considered by Reynolds et al 35 These authors suggest that in order to improve the agreement it is necessary to include admixtures of the excited level 2 F 7/2 in the ground level 2 F 5/2 ͑recall that the 2 F 7/2 level lies within ϳ2200 cm Ϫ1 of the ground state͒. A mechanism is provided by the static crystal-field potential which, since it contains terms in A 6 6 ͑crystal-field parameter͒, leads to mixing of levels differing in J z by Ϯ6.…”

Atomic level stress and light emission of Ce activated SrS thin films

“…In the case of the cubic symmetry, EPR transitions in the ⌫ 7 doublet should give rise to a single line spectrum with an isotropic g value of ͉10/7ϭ1.4286͉. 10,11 Indeed, as displayed in Fig. 1, in Ce activated SrS powders with low Ce concentrations ͑Ͻ500 ppm͒, the EPR spectra do show an isotropic resonance at gϭ1.3086, characteristic of Ce 3ϩ ions located at a sixfold coordinated site having cubic symmetry.…”

“…1, in Ce activated SrS powders with low Ce concentrations ͑Ͻ500 ppm͒, the EPR spectra do show an isotropic resonance at gϭ1.3086, characteristic of Ce 3ϩ ions located at a sixfold coordinated site having cubic symmetry. [6][7][8]10,11 The EPR of the Ce 3ϩ ion in the SrS:Ce thin films is different from that observed in powders. For instance, the linewidth of the Ce 3ϩ resonance in the powders is 15 G, while it is 240 G for films deposited on borosilicate glass.…”