Study of the surrogate-reaction method applied to neutron-induced capture cross sections

Abstract

174Yb(3He,αγ )173Yb* and 174Yb(3He,pγ )176Lu*, respectively. For the first time, the gamma-decay probabilities have been obtained with two independent experimental methods based on the use of C6D6 scintillators and Germanium detectors. Our results for the radiative-capture cross sections are several times higher than the corresponding neutron-induced data. To explain these differences, we have used our gamma-decay probabilities to extract rather direct information on the spin distributions populated in the transfer reactions used. They are about two times wider and the mean values are 3 to 4 ¯h higher than the ones populated in the neutron-induced reactions. As a consequence, in the transfer reactions neutron emission to the ground and first excited states of the residual nucleus is strongly suppressed and gamma-decay is considerably enhanced

Spin differences in the Zr90 compound nucleus induced by (p,p′) , Ota1, Burke2, Casperson3 et al. 2015Phys. Rev. C233280View full textAdd to dashboardCite

“…Many experiments have shown a trend that the surrogate reactions tend to preferably populate higher J than the direct measurements using neutron beams [15,21,24]. The present results indicate that (p, p ) populates much lower J states than (p, d) and (p, t), therefore it is possible that (p, p ) provides a better surrogate for the direct measurements than (p, d) and (p, t) reactions.…”

“…While this has a smaller effect on the extraction of fission cross sections [9], the γ-ray emission of the compound nucleus can be quite sensitive to the initial J π distribution [14,15,[17][18][19][20][21]. Therefore, in order to extract (n, γ) cross sections from surrogate data it becomes necessary to take into account the J π distribution of the decaying compound nucleus.…”

“…Specifically, we compare P i for γ-ray transitions in 90,89 Zr, following the production via inelastic (p, p ), (p, p n) scattering, and (p, d), (p, dn) and (p, t), (p, tn) transfer reactions. Earlier studies suggest that the direct reactions typically used in surrogate experiments transfer more units of angular momentum (∆L) to the compound nucleus than the neutron does in the desired reaction [15,21,24]. For 158 Gd, it was estimated that (p, d) and (p, t) reactions transfer ∆L = 4 and ∆L = 5 , respectively, in the quasi-continuum region (E x =3.5-5 MeV) [24], and describing the data obtained in inelastic proton scattering on gadolinium seems to require similarly large ∆L transfers.…”

First simultaneous measurement of fission and gamma probabilities of237U and239Np via surrogate reactions

“…[4]) showed a very good agreement of the fission cross sections obtained with the surrogate and direct methods for actinides. However, in recent experiments [5,6] radiative capture cross sections on rare earths obtained in surrogate reactions were found to be higher up to a factor of 10 than the corresponding neutron-induced reaction data. These important discrepancies were attributed to the large differences in the angular momentum between the mother and the daughter nuclei around the neutron separation energy, which results in the hindering of the neutron emission channel and therefore in the increase of the gamma emission probability [6].…”

87Y(n,γ) and89,90Zr(n,γ) cross sections from a surrogate reaction approach

“…While the applicability of the surrogate reaction approach has been demonstrated for (n,f) cross sections [8][9][10][11][12], it has been difficult to determine (n,J) cross sections due primarily to the discrepancy in the spin-parity distributions of the compound nucleus created by the (n,J) and the surrogate reaction [13][14][15][16][17]. However, some recent research showed promise for inferring (n,J) cross sections by accounting for spin-parity distribution of the compound nucleus [18].…”