Conduction electron density at the nucleus in Sm and Dy metal

doi:10.1016/0375-9601(68)90206-5

Physics Letters A

Volume 28, Issue 3, 18 November 1968, Pages 209-211

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Abstract

From Mössbauer isomer shift measurements the conduction electron densities at the nucleus in Sm metal |ψ|²(C.E. Sm) = (+1.4 ± 0.4) × 10²⁶ cm⁻³ and in Dy metal |ψ|²(C.E. Dy) = (+1.65 ± 0.35) × 10²⁶ cm⁻³ deduced.

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Change of the nuclear charge radius in excitation of 2+ levels in ytterbium isotopes
1973, Nuclear Physics, Section A
Recoilless γ-ray spectroscopy was employed to study isomer shifts of 2⁺ ↔ 0⁺ rotational transitions in the ytterbium isotopes ^{170, 172, 174, 176}Yb. For ¹⁷⁰Yb conventional source experiments were performed, while for the other nuclei the method of recoil implantation through vacuum following Coulomb excitation was used to produce single line Mössbauer sources. For ¹⁷⁰Yb isomer shifts were measured for a series of divalent, trivalent, and metallic single line absorbers with mostly cubic symmetry. In addition the eflect of interference between resonant nuclear absorption followed by internal conversion and photoelectric absorption was observed. For the dispersion term a weighted mean of 2ξ = −0.030±0.004 was derived. In the implantation experiments isomer shifts were measured between highly enriched absorbers of YbF₂ and Yb₂S₃. From the measured differences in isomer shifts the following ratios were derived: $Δ〈r^{2} 〉_{172} Δ〈r^{2} 〉_{170} = 0.34±0.08$ , $Δ〈r^{2} 〉_{174} Δ〈r^{2} 〉_{170} = −0.37±0.07$ , $lΔ〈r^{2} 〉_{176} Δ〈r^{2} 〉_{170} = −0.14±0.04$ . For an electron density difference of Δ|ψ|² = 4.0±1.2×10²⁶ cm⁻³ between Yb³⁺ and Yb²⁺, as derived from optical isotope shift data for Yb and Sm ions, the following absolute values of Δ〈r²〉 were obtained: Δ〈r²〉₁₇₀ = 1.20±0.40×10⁻³ fm², Δ〈r²〉₁₇₂ = 0.41±0.20 x10⁻³ fm², Δ〈r²〉₁₇₄ = −0.44±0.19x10⁻³ fm², Δ〈r²〉₁₇₆ = −0.17±0.10× 10⁻ fm². This marked dependence of Δ〈r²〉 on the neutron number is especially striking in view of the constancy of nuclear deformation in this series of ytterbium isotopes, but it is in good agreement with the predictions of a recent microscopic theory of Meyer and Speth.
The contribution of 5d electrons to the saturation magnetic moments and magnetic hyperfine fields in the heavy rare earth metals
1973, Solid State Communications
The main results of a model for 5d electrons in the heavy rare earth metals are presented. The model involves the use of wave functions based on published analyses for 4fⁿ5d6s² atomic configurations, and the spreading of each of these energy levels uniformly over a band of width W in the metals. Excess saturation magnetic moments above those of the tripositive ions can be explained by the model with W in the range 0.84±0.16eV in the five metals Gd, Tb, Dy, Er and Tm. The magnetic hyperfine fields in the metals include negative contributions from the 5d electrons which have been shown to amount to about −250koe in Gd, Er and Tm.
Study of the Mössbauer effect in europium and dysprosium chelates
1971, Journal of Inorganic and Nuclear Chemistry
The results of Mössbauer studies for several europium and dysprosium chelates are reported. From the values obtained for the isomer shifts it may be concluded that the covalent bonding admixture can be explained by the transfer of electrons from the ligands to the partly filled 4f shell in Eu³⁺ and Dy³⁺. From the known values of the isomer shifts between Eu²⁺ and Eu³⁺ and between Dy²⁺ and Dy³⁺ it can be concluded that in the chelates studied the covalent bonding contribution to the bonding amounts to about 4 per cent.
Calculation of the conduction electron density at the nucleus in dysprosium metal
1971, Solid State Communications
The density of conduction electrons at the nucleus in dysprosium metal has been calculated following the nonrelativistic APW formalism. The agreement of this quantity with that obtained from the Mössbauer isomeric shift is good if proper account of the relativistic effect is taken into consideration.
La densité des électrons de conduction au noyau du métal de Dysprosium a été calculée dans le formalisme non relativiste APW. L'accord de cette quantité avec celle obtenue à partir du déplacement isomérique de Mossbauer est bon si l'on tient compte correctement de l'effet relativiste.
Recoilless absorption measurements of the 25.6 keV gamma-rays of 161Dy emitted from four-valent dysprosium ions
1970, Physics Letters A
Isomer shift of the 2+ state in 160Gd and 158Gd from recoil implantation Mössbauer studies
1970, Physics Letters B
The Mössbauer effect observed after recoil implantation of Coulomb excited nuclei has been used to measure the change in nuclear charge radius in the 2⁺ → 0⁺ rotational transition of ¹⁶⁰Gd and ¹⁵⁸Gd. The results (Δ〈r²〉/〈r²〉)₁₅₈ = 0.6 ± 0.3) × 10⁻⁴ and (Δ〈r²〉/〈r²〉)₁₆₀ = (0.1 ± 0.3) × 10⁻⁴ agree with theoretical predictions and indicate the presence of centrifugal stretching.

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Physics Letters A

Abstract

References (6)

Rev. Mod. Phys.

Z. Physik

Phys. Letters

Cited by (15)

Change of the nuclear charge radius in excitation of 2<sup>+</sup> levels in ytterbium isotopes

The contribution of 5d electrons to the saturation magnetic moments and magnetic hyperfine fields in the heavy rare earth metals

Study of the Mössbauer effect in europium and dysprosium chelates

Calculation of the conduction electron density at the nucleus in dysprosium metal

Recoilless absorption measurements of the 25.6 keV gamma-rays of <sup>161</sup>Dy emitted from four-valent dysprosium ions

Isomer shift of the 2<sup>+</sup> state in <sup>160</sup>Gd and <sup>158</sup>Gd from recoil implantation Mössbauer studies