[en] A method is provided for selective photoionization of the odd-numbered atomic mass gadolinium isotopes 155 and 157. The selective photoionization is accomplished by circular or linear parallel polarized laser beam energy effecting a three-step photoionization pathway

[en] Using ¹⁵⁵Gd Moessbauer spectroscopy down to 27 mK, we show that, in the geometrically frustrated pyrochlore Gd₂Sn₂O₇, the Gd³⁺ hyperfine levels are populated out of equilibrium. From this, we deduce that the hyperfine field, and the correlated Gd³⁺ moments which produce this field, continue to fluctuate as T -> 0. With a model of a spin 1/2 system experiencing a magnetic field which reverses randomly in time, we obtain an analytical expression for the steady state probability distribution of the level populations. This distribution is a simple function of the ratio of the nuclear spin relaxation time to the average electronic spin-flip time. In Gd₂Sn₂O₇, we find the two time scales are of the same order of magnitude. We discuss the mechanism giving rise to the nuclear spin relaxation and the influence of the electronic spin fluctuations on the hyperfine specific heat. The corresponding low temperature measurements in Gd₂Ti₂O₇ are presented and discussed. (authors)

[en] The p- and d-neutron strength functions of ¹⁵⁵Gd:S_nl=(1.35±0.11)x10^-4, S_n2=(1.87±0.40)x10^-4, as well as the M1- and E2-radiative strength functions, were determined from the analysis of the primary γ-ray intensities in the ¹⁵⁵Gd(n, γ) reaction at E_n=1.9, 3.5, 45, 59 and 134 keV average neutron energies. The spin splitting effect of the s-neutron strength function S_n0 was investigated. The S_n0 splitting was not observed out of the experimental errors. 15 refs.; 4 figs.; 2 tabs

[en] Although four decades ago it had been conclusively shown that the first excited 0₂⁺ state in ¹⁵⁶₆₆Dy⁹⁰ was a pairing isomer, the lessons of this identification has taken a long time to connect with the Nuclear Structure Community. The 0₂⁺ states that can be populated significantly with two particle neutron transfer, all have large enough cross-sections to demonstrate that simple monopole pairing in theoretical descriptions will be insufficient. The conclusion that these states cannot be associated with time-dependent β vibrations of the nuclear shape is also supported by their very weak excitation in inelastic scattering processes such as (d,d'). Blocking of the coupling of the single particle neutrons in odd nuclei to the 0₂⁺ states near N=90 have shown that a major part of their configurations is a pair of neutrons in the [505]11/2^- Nilsson orbit. This high-K orbit is extruded from the h_11/2 shell to the Fermi surface by the increasing deformation caused by adding neutrons outside the N=82 core. These data confirm the separation of prolate-prolate and oblate-oblate pairing. At iThemba LABS we have used conventional γ-ray spectroscopy to investigate structures in the pairing gaps of even-even nuclei in the ranges Z=62-70 and N=88-92, in particular to study the systematics of the excited Kπ = 0₂⁺2 and 2_γ⁺ positive parity bands. We find that the 02+ bands all have moments-of-inertia that are greater than those of the ground state 0₁⁺1 bands, in complete contradiction to the predictions of all Interacting Boson Models (IBM). The larger moments-of-inertia for 0₂⁺ bands are consistent with reduced pairing due to the low density of oblate (high-W) orbitals near the Fermi surface. The odd spin members of the γ bands all track the ground state bands while the even spin members can mix with the 0₁⁺ and 0₂⁺ bands. Indeed the γ bands and 0₂⁺ bands cross and interact strongly affecting the signature splittings S(I) observed in the γ bands. The systematic data will be discussed in terms of the Triaxial Projected Shell Model (TPSM) and the 5-Dimensional Collective Model (5-DCM). This document is composed of an abstract and the slides of the presentation. (author)

[en] ¹⁵⁵Gd was produced in the ¹⁵⁰Nd(¹²C,α3n) reaction at 65 MeV. A partial level scheme constructed from γ-γ coincidence measurements is shown, and rotational bands are labeled. The ground-state rotational band in ¹⁵⁶Gd is also presented

No abstract available

[en] It was shown by means of ¹⁵⁵ Gd Moessbauer spectroscopy that the peculiarities in the PrBa₂Cu₃O₇ compound's behaviour could be explained assuming the mutual substitution of the Pr³⁺ and Ba²⁺ ions in the mentioned lattice. (author). 8 refs., 1 fig

No abstract available

[en] The neutron capture cross-sections and the capture -ray spectra of 155Gd and 157Gd were measured at the 3-MeV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo Institute of Technology in the energy range from 10 to 550 keV. Pulsed keV-neutrons were produced from the 7Li(p,n)7Be reaction by bombarding the lithium target with the 1.5-ns bunched proton beam from the Pelletron accelerator. The spectrum for the neutrons incident on a capture sample was measured by means of a time-of-flight method with a 6Li-glass detector. Capture - rays were detected with a large anti-Compton NaI(Tl) spectrometer by employing a time-of-flight method. A pulse-height weighting technique was applied to the observed capture -ray pulse-height spectra to derive the capture yields. The neutron capture cross-sections were determined relative to the standard capture cross-section of 197Au. The results were compared to other measurements and the evaluated values. The capture -ray spectra were obtained by unfolding the observed capture -ray pulse-height spectra.

[en] The intensities of primary γ transitions in the reaction ¹⁵⁵Gd(n,γ) at average neutron energies E_n=1.9, 3.5, 45, 59, and 134 keV are analyzed with the aim of determining the p- and d-neutron strength functions of ¹⁵⁵Gd and the M1 and E2 radiative strength functions. The former are found to be S_n1 = (1.35 ± 0.11) x 10^-4 and S_n2 = (1.87 ± 0.40)x10^-4. The effect of spin splitting of the s-neutron strength function S_nO is studied. No spin splitting of S_nO falling beyond experimental errors is found: a=(S⁺_n0 - S^-_n0)/S_n0=0.16 ± 0.33. 15 refs., 4 figs., 2 tabs