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[en] Experimental data on "9"1","9"4Zr photodisintegration that were obtained in a beam of quasimonoenergetic annihilation photons by the method of neutron multiplicity sorting are analyzed. It is found that the cross sections for the (γ, 1n), (γ, 2n), and (γ, 3n) reactions on both isotopes do not meet the objective data-reliability criteria formulated earlier. Within the experimental–theoretical method for evaluating partial-reaction cross sections that satisfy these criteria, new data on the cross sections for the aforementioned partial reactions, as well as for the (γ, sn) = (γ, 1n) + (γ, 2n) + (γ, 3n) +... total photoneutron reaction, are obtained for the isotopes "9"1","9"4Zr
[en] Lifetimes of excited states in 94Zr were previously measured applying the Doppler-shift attenuation method (DSAM) following the (n,n'γ) reaction.Since the two measurements were in conflict with each other, we remeasured 14 lifetimes of excited states in 94Zr in a (p,p'γ) experiment utilizing the DSAM technique. Centroid-energy shifts were extracted from proton-gated γ-ray spectra, yielding lifetime values that are independent of feeding contributions. The results were compared to the previously measured lifetimes and found to be in good agreement with the values reported, thus confirming the correction procedure introduced for the (n,n'γ) data. This contribution features our new results and introduces the (p,p'γ) DSAM technique, which is now available in Cologne.
[en] The low-lying low-spin levels of 94Nb have been investigated; these levels were populated via the 94Zr(p,nγ)94Nb reaction with a separated isotope 94Zr foil target (96% 94Zr). Excitation functions of γ rays were obtained at incident proton energies from 1.688 to 3.700 MeV. γ-γ coincidences were observed at E/subp/=3.0 MeV. The existence of additional levels at 301.5, 450.3, 666.2, and 785.0 keV has been established. Computed Hauser-Feshbach (p,n') cross sections have been fitted to experimental cross sections deduced from the γ-ray data with the resulting best-fit spin-parities: 140.4-keV level, 2-; 301.5, 2-; 334.2, 3+; 396.3, 4-; and 450.3, 3+
[en] Recently, E. Elhami et al. (2008) reported on a study of the low-spin structure of 94Zr with the (n,n',γ) reaction. The author claimed observation of an anomalous situation where the E2 excitation strength of the mixed-symmetry 2+2 exceeds the strength of the symmetric 2+1 state. Those excitations of 94Zr have been investigated with electron scattering at the S-DALINAC and a model-independent analysis of our (e,e') data has been performed. The extracted ratio of the E2 strengths, B(E2,0+1 → 2+ms)/B(E2,0+1 → 2+1) is less than the unity, which contradicts the (n,n',γ) results. The data analysis and the results are presented. The same analysis has been applied to a set of electron scattering data on 94Mo. The ratio of the of B(E2) strengths of the symmetric and mixed-symmetry 2+ states in 94Mo and their transition radius difference have been extracted for the first time.
[en] In order to establish more accurate nuclear data for the zirconium isotopes 94Zr and 96Zr, joint experimental work has been conducted at three different reactor types. After carefully calibrating the neutron spectra in the irradiation channels used, nuclear constants ksub(o) and Qsub(o) were remeasured and found to be ksub(o),sub(Au)(724 keV) = 9.321x10-5 (+- 0.6%); Qsub(o)(α = O) = 5.05 (+- 2.0%) for 94Zr(n,γ)95Zr. ksub(o,Au)(743 keV) = 1.296x10-5 (+- 0.9%); Qsub(o)(α = O) = 248.2 (+- 1.5%) for 96Zr(nγ)97Zr. The relevant effective resonance energies Esub(r) have been recalculated using the latest BNL neutron resonance parameters yielding Esub(r)94Zr)=6260 eV (+- 4%) and Esub(r)(96Zr)=338 eV (+- 2%). The epithermal neutron shielding factor Gsub(e) has been experimentally determined as a function of foil thickness. The results gave Gsub(e)(94Zr)=0.983 (+- 0.3%) and Gsub(e)(96Zr)=0.973 (+- 0.4%) for the most frequently used 0.125 mm foil thickness. Finally the half life of the 97Zr isotope has also been remeasured to give Tsub(half)(97Zr)=16.744 +- 0.011 h with 1 σ limit. (author)
[en] A thin isotopic 94Zr target of thickness 520μg/cm2 has been prepared for recoil distance Doppler shift method (RDM) lifetime measurement by using an electron beam deposition method on tantalum backing of 3.5 mg/cm2 thickness at Inter University Accelerator Center (IUAC), New Delhi. To meet the special requirement of smoothness of surface for RDM lifetime measurement and also to protect the outer layer of 94Zr from peeling off, a very thin layer of gold has been evaporated on a 94Zr target on a specially designed substrate holder. In all, 143 mg of 99.6% enriched 94Zr target material was utilized for the fabrication of 94Zr targets. The target has been successfully used in a recent RDM lifetime measurement experiment at IUAC
[en] The aim of the activity was to make a thin target of isotopically enriched 94Zr for lifetime measurement experiment to be done with the plunger setup at the Inter University Accelerator Center (IUAC) Delhi