Cross sections for the formation of69Znm,gand

Abstract

Excitation functions were measured for the reactions 72 Ge(n,␣) 69 Zn m,g , 69 Ga(n,p) 69 Zn m,g , 70 Zn(n,2n) 69 Zn m,g , 74 Ge(n,␣) 71 Zn m,g , and 71 Ga(n,p) 71 Zn m,g over the neutron energy range of 6.3-12.4 MeV. Quasimonoenergetic neutrons in this energy range were produced via the 2 H(d,n) 3 He reaction using a deuterium gas target at the Jülich variable energy compact cyclotron. Use was made of the activation technique in combination with high-resolution HPGe-detector ␥-ray spectroscopy. In a few cases low-level ␤ Ϫ counting was also applied. In order to decrease the interfering activities in those cases, either radiochemical separations were performed or isotopically enriched targets were used. For most of the reactions, the present measurements provide the first consistent sets of data near their thresholds. From the available experimental data, isomeric cross-section ratios were determined for the isomeric pair 69 Zn m,g in (n,␣), (n,p), and (n,2n) reactions, and for the pair 71 Zn m,g in (n,␣) and (n,p) reactions. Nuclear model calculations using the code STAPRE, which employs the Hauser-Feshbach ͑statistical model͒ and exciton model ͑precompound effects͒ formalisms, were undertaken to describe the formation of both isomeric and ground states of the products. The calculational results on the total (n,␣), (n,p), and (n,2n) cross sections agree fairly well with the experimental data. The experimental isomeric cross-section ratios, however, are reproduced only approximately by the calculation. For both the isomeric pairs investigated, the isomeric cross-section ratio in the (n,p) reaction is higher than in other reactions.

Cross-section measurements of neutron-induced reactions on GaAs using monoenergetic beams from 7.5 to 15 MeV

“…The difference in the cross-section values might stem out from any of these factors. For the 69 Ga(n, p) 69 Zn m reaction, the measured cross-sections in the present work are in good agreement with the results of Nesaraja et al [2], within the uncertainties quoted by the latter. The results from Pu et al [8] at a single energy is discrepant with respect to the shape of the excitation function set by the present measurements as well as that by Nesaraja et al.…”

“…As far as the 71 Ga(n, p) 71 Zn m reaction is concerned, the cross-section values from the present measurements agree with those of Nesaraja et al [2], only with substantially lower uncertainties than the latter. The present measurements also agree well with the measurements of Pu et al [8] and Qaim et al [20] around 14 MeV while that of Vinitskaya et al [21] is somewhat low, though overlapping with the present measurements within the quoted uncertainty.…”

“…However, our determination of the breakup contribution is based on the actual measurements of the neutron spectra and agrees with the observations of Birn et al [4] for the 75 As(n, p) 75 Ge and the 75 As(n, 2n) 74 As reactions. In the latest published results for the 69 Ga(n, p) 69 Zn m and 71 Ga(n, p) 71 Zn m reactions, Nesaraja et al [2,3] quoted only the wide range of 1-10% for the size of the correction due to break-up neutrons. This is consistent with our observations.…”

“…Nesaraja et al [2,3] studied 71 Ga(n, p) 71 Zn m and 69 Ga(n, p) 69 Zn m reactions in the energy range from 6.2 MeV to 12.4 MeV using the activation technique. They reported cross-section values with uncertainties of 9-20%, with most of the uncertainties coming from counting statistics and the radiochemical procedures employed to isolate the activated products of interest from the matrix activity.…”

Evaluation of neutron nuclear data for gallium

“…On the whole, the present statistical-model calculations are in good agreement with experimental data except for a few cases. The 69 Ga(n, p) 69g Zn cross sections, which were measured by Nesaraja et al [58] using an enriched sample (0.46% for 69 Ga and 99.54% for 71 Ga) and β − counting in the energy region from 6 to 12 MeV, are not reproduced by all the evaluations, although the evaluations are consistent with the measurement of Demichelis et al [59] Concerning the 71 Ga(n, p) 71g Zn reaction, the present evaluation laid weight on the measurements of Nesaraja et al [58], whereas JENDL/A-96 and JEFF-3.1/A are obviously based on the data of Molla and Qaim [60]. As for the 71 Ga(n, nα) 67 Cu reaction, both the present and JENDL-4.0 evaluations are smaller than the experimental data of Bormann et al [61] above 15 MeV, although those evaluations are almost consistent with the other measurements around 14 MeV.…”