D. Dehnhard

Elastic transfer in the scattering of 16O by 28Si

Abstract It is shown that the interference of potential scattering and elastic transfer amplitudes can account for the recently observed gross structure in the excitation function for elastic scattering of 16O by 28Si at 180°.

Potential description of elastic scattering of 28Si+16O between 45 and 63 MeV

Abstract Excellent fits to extensive elastic scattering data for 28 Si+ 16 O measured between 45 and 63 MeV were obtained with energy-dependent, surface-transparent optical potentials without explicitly resorting to a Regge-pole type analysis; S -matrix elements derived from the two analysis are completely different.

Neutron-proton radius differences and isovector deformations from π+ and π− inelastic scattering from 18O

Abstract π+ and π− elastic and inelastic scattering from 18O have been measured at T(π)=164 MeV. Consistent with the results at 230 MeV, it is found that the ratio σ(π − ) σ(π + ) for the 21+ state is 1.86(16), while for the 31− state it is 0.89(6). These results are interpreted as indicating differences in neutron and proton deformations characterizing the 21+ transition and partial neutron blocking for the 31− transition. Optical model analysis of elastic scattering leads to the conclusion that 〈r n 2 〉 1 2 −〈r p 2 〉 1 2 =0.03(3) fm .

A comparative study of the 13C(p, p′)13C and 13C(p, n)13N reactions at Ep = 35 MeV☆

Abstract Differential cross sections were measured at Ep = 35 MeV for the 13C(p, n) and 13C(p, p′) reactions leading to the four low-lying states in the mirror nuclei 13N and 13C. In addition, the analyzing powers were measured for the 13C(p, p′) reaction. The data are generally well accounted for by DWBA calculations except for the 13 C(p, p′) 13 C (3.09 MeV , 1 2 + ) reaction, for which the calculations cannot even reproduce the qualitative features of the data. A comparison of the (p, n) and the (p, p′) results suggests that the isoscalar part of the 13 C ( g.s. , 1 2 − ) → 13 C (3.09 MeV , 1 2 + ) transition is not correctly described by currently available shell-model wave functions.

The j-dependence of the (19F, 16O) reaction☆

Abstract The total angular momentum transfer (j) dependence was studied for orbital angular momentum transfers l = 1, 2, and 3 in the (19F, 16O) reactions on 28, 30Si and 60Ni. In contrast to the strong j-dependence for the l = 2 transitions to 31, 33P states, no distinct j-dependence was found for the l = 1 and l = 3 transitions to 63Cu states. Previously reported results for the 28 Si ( 19 F , 16 O) 31 P reaction were re-analyzed using optical-potential sets which fit the elastic-scattering data for both the entrance and exit channels. Results of DWBA calculations without use of spin-orbit potentials were found to be out of phase with the data for all l-transfers and the j-dependence could not be reproduced. Both of these problems were alleviated by including spin-orbit forces in the optical potentials. However, a good fit to the 28Si(19F, 16O)31P data was obtained only if the optical potentials that fit the elastic scattering data were modified for the exit channel.

Pion-nucleus interactions: Experiments

Abstract Recent experimental results on pion-nucleus elastic and inelastic scattering and pion-induced single — and double-charge-exchange reactions are discussed.

Proton occupation numbers for 44Ca

Abstract The (d, 3 He) proton pickup reaction on 44 Ca has been studied at a deuteron energy of E d = 19.0 MeV using the Minnesota MP Tandem Van de Graaff. Differential cross sections were measured at forward angles and spectroscopic factors were extracted in the usual fashion for the transitions to five states of 43 K. The results are compared with previous proton pickup and stripping reactions on the even Ca isotopes. Only about half of the sd hole state excitation strength observed in the stripping reactions could be found in the pickup from the fp orbitals if the data are analyzed by standard distorted wave calculations. This discrepancy can be removed by using bound state potential radii which are slightly larger for sd orbitals than for fp orbitals.

The 17,18O(p, n)17,18F reaction at Ep = 35 MeV

Abstract The 17,18 O(p, n) 17,18 F reactions were studied at E p = 35 MeV. Neutron spectra were measured at laboratory angles between 0° and 140°. Results were compared with distorted-wave calculations using the shell-model wave functions. For the 17 O(p, n) reaction, cross-section magnitudes as well as the angular-distribution shapes were well described by the calculation. On the other hand, normalization factors of 0.60 were required for the spin-flip excitations observed in the 18 O(p, n) reaction leading to the ground (1 + ), 1.700 MeV (1 + ) and 2.100 MeV (2 − ) states. Possible origins of such differences were discussed.

The 16O(p,p′) reaction at 35 MeV

Abstract The 16O( p , p ′ ) reaction was studied with a 35 MeV polarized proton beam. The cross sections and analyzing powers for excited states in 16O up to and including the 2−, T = 1 state at 12.97 MeV were measured and compared with DWBA calculations. Both density-independent and densitydependent effective interactions were used in the calculations. Transition densities calculated using shell-model amplitudes and Woods-Saxon single-particle wave functions give poor accounts of the data. The use of macroscopic transition densities obtained from electron scattering data give a much better description of the data, especially when used in combination with the densitydependent interaction.

Equilibrium charge-state distributions for 16O ions at 20–65 MeV

Abstract Equilibrium charge-state distributions for 20–65 MeV 16 O ions scattered off carbon-backed gold targets were measured. Significant differences were found between the experimental results and calculated values based on the semi-empirical theory of Zaidins.