Neutrons from 9Be/alpha,n/ reaction for E alpha between 6 and 10 MeV

Neutron energy spectra measured as function of neutron emission angle and ion bombardment energ

Reaction channel contributions to the helion optical potential

Background: The well-established coupled channel and coupled reaction channel processes contributing to direct reactions make particular contributions to elastic scattering that are absent from local density folding models. Very little has been established concerning the contribution of these processes to the optical model potentials (OMPs) for 3He scattering. For studying such processes, spin-saturated closed shell nuclei such as 16O and 40Ca are particularly suitable target nuclei and the (3He, 4He) reaction is easily handled within conventional reaction theory because it avoids complications such as breakup.Purpose: To establish and characterize the contribution to the 3He-nucleus interaction generated by coupling to neutron pickup (outgoing 4He) channels; also to study the contribution of collective states and identify effects of dynamical nonlocality from these couplings.Methods: Coupled reaction channel (CRC) calculations, including coupling to collective states, will provide the elastic channel S-matrix Sl j resulting from the included processes. Inversion of Sl j will produce the local potential that yields, in a single channel calculation, the elastic scattering observables from the coupled channel calculation. Subtracting the bare potential from the CRC calculations yields a local and l-independent representation of the dynamical polarization potential (DPP). From the DPPs, because of a range of combinations of channel couplings, the influence of dynamically generated nonlocality can be identified.Results: Coupling to 4He channels systematically induces repulsion and absorption in the 3He OMP and also a reduction in the rms radius of the real part. The repulsion and absorption is less for 208Pb than for the lighter target nuclei although the qualitative effects, including the general undularity of the DPPs, are similar for all cases; therefore coupling to these channels cannot be represented by renormalizing folding model potentials. Evidence is presented for substantial dynamical nonlocality of the induced DPPs; for 40Ca this modifies direct reaction angular distributions. The local equivalent DPPs for individual couplings cannot be added to give the overall DPP for the complete set of couplings. For the 208Pb case, channel coupling reduces the reaction cross section although it increases it for 16O, with 40Ca an intermediate case. Conclusions: The DPPs established here strongly challenge the notion that folding models, in particular local density models, provide a satisfactory description of elastic scattering of 3He from nuclei. Coupling to neutron pickup channels induces dynamical nonlocality in the 3He OMP with implications for direct reactions involving 3He. Departures from a smooth radial form for the 3He OMP should be apparent in good fits to suitable elastic scattering data

Survey of ground state neutron Spectroscopic Factors from Li to Cr isotopes

The ground state neutron spectroscopic factors for 80 nuclei ranging in Z from 3 to 24 have been extracted by analyzing the past measurements of the angular distributions from (d,p) and (p,d) reactions. We demonstrate an approach that provides systematic and consistent values with minimum assumptions. For the 61 nuclei that have been described by large-basis shell-model calculations, most experimental spectroscopic factors are reproduced to within 20%.Comment: 12 pages, 2 figures, 2 table

Many-body effects in 16O(e,e'p)

Effects of nucleon-nucleon correlations on exclusive $(e,e'p)$ reactions on closed-shell nuclei leading to single-hole states are studied using $^{16}O(e,e'p)^{15}N$ ($6.32$ MeV, $3/2^-$) as an example. The quasi-hole wave function, calculated from the overlap of translationally invariant many-body variational wave functions containing realistic spatial, spin and isospin correlations, seems to describe the initial state of the struck proton accurately inside the nucleus, however it is too large at the surface. The effect of short-range correlations on the final state is found to be largely cancelled by the increase in the transparency for the struck proton. It is estimated that the values of the spectroscopic factors obtained with the DWIA may increase by a few percent due to correlation effects in the final state.Comment: 21 Pages, PHY-7849-TH-9

Calculations of three-body observables in ^8B breakup

We discuss calculations of three-body observables for the breakup of ^8B on a ^{58}Ni target at low energy using the coupled discretised continuum channels approach. Calculations of both the angular distribution of the ^7Be fragments and their energy distributions are compared with those measured at several laboratory angles. In these observables there is interference between the breakup amplitudes from different spin-parity excitations of the projectile. The resulting angle and the energy distributions reveal the importance of the higher-order continuum state couplings for an understanding of the measurements.Comment: 22 pages (postscript), accepted in Phys. Rev.

A Microscopic T-Violating Optical Potential: Implications for Neutron-Transmission Experiments

We derive a T-violating P-conserving optical potential for neutron-nucleus scattering, starting from a uniquely determined two-body $\rho$-exchange interaction with the same symmetry. We then obtain limits on the T-violating $\rho$-nucleon coupling $\overline{g}_{\rho}$ from neutron-transmission experiments in $^{165}$Ho. The limits may soon compete with those from measurements of atomic electric-dipole moments.Comment: 8 pages, 2 uuencoded figures in separate files (replaces version sent earlier in the day with figures attached), in RevTeX 3, submitted to PR