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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.

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The three values quoted in the abstract for the dielectron widths (ÿ ee ) are actually the respective values for ÿ ee ÿ had =ÿ tot . The correct dielectron widths are given in Table II of the text: 1:354 0:004 0:020 keV for the 1S, 0:619 0:004 0:010 keV for the 2S, and 0:446 0:004 0:007 keV for the 3S.

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