Effects of deformation on neutron total cross sections of even-ANd and Sm isotopes

Abstract

Sm have been measured at 25 energies from 0.75 to 14 MeV. Each sample consisted of about 40 g of powdered oxide with an isotopic enrichment & 94/o.For each isotopic pair the total cross-section difference was determined directly by measuring the ratio of transmitted flux for matched samples. This difference was'found to have an oscillatory behavior when plotted as a function of incident neutron energy. The oscillations have been explained as a deformation effect qualitatively in terms of the nuclear Ramsauer effect and quantitatively using a deformed optical model potential. Adding two neutrons to a nucleus in this mass region was found to have a different effect on the neutron total cross section than adding two protons. A coupled channel analysis was performed using as input data the present total cross sections, low-energy neutron scattering parameters, and elastic and inelastic (2+) differential cross sections for neutron scattering at 4 and 7 McV. Excellent total cross-section fits were obtained for the Sm isotopes; however, the total cross-section fits for the Nd isotopes were only fair. Quadrupole deformation parameters have been deduced for all the isotopes studied. The sensitivity of neutron total cross-section differences to this parameter and to the real isospin term of the nuclear potential is discussed. gUCLEAH REACTIONS i42'~44'i @ 48'~~ONd, E"=0.75-13.89 MeV, i~0'~52'i Sm, E"=0.75-14.49 MeV; measured o'" tpt{E). Enriched targets. Deduced coupledchannel optical-potential parameters, quadrupole deformation parameters.

EVALUATION OF NEUTRON CROSS SECTIONS FOR A COMPLETE SET OF Nd ISOTOPES.

“…Our results are discussed below, shown later are Figs. 8 and 10 confirming that calculated total cross sections reproduce the reported experimental data [43][44][45].…”

“…Cross Section (b) [16,43,44]. Our coupled-channels calculations are divergent below 1 MeV and tend to approach each other above.…”

“…There are measurements by Wisshak et al [16] in the unresolved resonance region and by Shamu et al [43] from 0.7 MeV up to 14 MeV, and a single-energy point by Djumin et al [44] at 14.2 MeV. In addition, there is the measurement of the elastic angular distribution at 7.0 MeV by Haouat et al [45].…”

Octupole correlations in the structure of02+bands in theN=88nuclei150Bvumbi1, Sharpey‐Schafer2, Jones3 et al. 2013Phys. Rev. C27180View full textAdd to dashboardCite

“…These data demonstrate that the N = 88 nuclei, 148 Nd and 150 Sm, are weakly deformed. This is confirmed by measurements of total neutron cross sections for the Nd and Sm isotopes [14] and by Coulomb excitation experiments [15]. The N = 88 nuclei with less than 60 protons, that have been investigated using fission fragment spectroscopy, have been suggested as candidates for having a static octupole deformation at medium spins [16][17][18].…”

Is a global coupled-channel dispersive optical model potential for actinides feasible?

“…It is generally accepted that differences of neutron total cross sections among neighboring nuclei provide an unusually stringent test of optical models [1][2][3][4]. At the same time it has been shown that the standard optical model treatment fails to reproduce the observed differences of total cross sections both for tungsten isotopes [4] and Th-U nuclei [5].…”