J. P. Schiffer

Production of radioactive ion beams using the in-flight technique

Reactions with a heavy projectile incident on a light target can be used for the efficient in-flight production of secondary radioactive beams. An overview of this technique is given using data on 17F beams produced via the p(17O, 17F)n and d(16O, 17F)n reactions. With primary 16,17O beam currents of 100 pnA, intensities of up to 2×106 17F/s on target were achieved. Using this beam, the p(17F,α)14O reaction was measured.

The neutron radius of 208Pb

Abstract A simple method is presented for calculating the radius of the neutron distribution of a nucleus from the energy of the isobaric analog state and the charge radius. The r.m.s. radius of the neutron distribution of 208Pb is calculated using the experimentally determined r.m.s. charge radius of 5.51 fm and the Coulomb displacement energy of 18.98 MeV. An r.m.s. neutron radius larger than the proton radius by 0.07 ± 0.03 fm is obtained.

Proton widths in a diffuse well

Abstract Widths have been calculated for resonant scattering of protons by a Woods-Saxon potential with accepted parameters. It is found that the single-particle estimate is only about one-quarter to one half of the Wigner-Teichman estimate for a radius of about 1.5 A 1 3 fm . This brings observed widths closer to the single-particle widths for certain levels expected to be single-particle levels in the shell model.

Nuclear structure relevant to neutrinoless double beta decay: 76Ge and 76Se.

The possibility of observing neutrinoless double beta decay offers the opportunity of determining the effective neutrino mass if the nuclear matrix element were known. Theoretical calculations are uncertain, and measurements of the occupations of valence orbits by nucleons active in the decay can be important. The occupation of valence neutron orbits in the ground states of 76Ge (a candidate for such decay) and 76Se (the daughter nucleus) were determined by precisely measuring cross sections for both neutron-adding and removing transfer reactions. Our results indicate that the Fermi surface is much more diffuse than in theoretical calculations. We find that the populations of at least three orbits change significantly between these two ground states while in the calculations, the changes are confined primarily to one orbit.

The {sup 8}B neutrino spectrum

Knowledge of the energy spectrum of {sup 8}B neutrinos is important for interpreting experiments that detect energetic neutrinos from the Sun. The neutrino spectrum deviates from the allowed {beta}-decay approximation because of the broad {alpha}-unstable {sup 8}Be final state and recoil order corrections. We have measured the total energy of the {alpha} particles emitted following the {beta} decay of {sup 8}B. The measured {alpha} spectrum is inconsistent with a recent measurement of comparable precision. The {alpha} spectrum is fit using the R-matrix approach, which gives a functional form for the {beta}-decay strength function for the transition from {sup 8}B to the accessible excitation energies in {sup 8}Be. Both the positron and neutrino energy spectra, corrected for recoil order effects, are constructed from the strength function. The positron spectrum is in good agreement with a previous direct measurement. The neutrino spectrum disagrees with previous experiments.

The (d, n) reaction on 24Mg and 28Si

Abstract The reactions 24 Mg(d, n) 25 Al and 28 Si(d, n) 29 P were studied. The J -dependent effects similar to those observed in (d, p) reactions were seen. Pronounced differences in neutron distributions resulting from I p = 2 transitions to the 1.36( 3 2 + ) and 1.96( 5 2 + ) MeV states in 29 P and to the ground state ( 5 2 + ) and 0.95 MeV state ( 3 2 + ) in 25 Al were noted. These differences were observed at incident deuteron energies of 7.0, 9.0 and 10.0 MeV. Absolute differential cross sections were determined for transitions to the states at 0, 0.45, 0.95, 1.79, 2.48, 2.68 and 3.06 MeV in 25 Al. Relative cross sections were determined for the states at 0, 1.36, 1.96 and 3.43 MeV in 29 P. The data were analysed by use of DWBA calculations and spectroscopic factors obtained for most of the above transitions. The results are compared with structure in the mirror nuclei 25 Mg and 29 Si.

91Zr(τ, α)90Zr and the T=1 g92−d52 matrix elements: Test of an average effective interaction

Abstract The 91Zr(τ, α)90Zr reaction has been studied and members of the ( g 9 2 ) −1 d 5 2 multiplet were identified, yielding the g 9 2 − d 5 2 particle-particle matrix elements in both isospin states. The results are compared with calculations using an interaction that had been deduced from other data.

Pion reaction modes on nuclei

Abstract The status of the overall features of recent inclusive data on pion-induced reactions on nuclei is summarized. Simple features of absorption and inelastic scattering are discussed.

Nuclear structure relevant to neutrinoless double β decay: The valence protons in Ge76 and Se76

The possibility of observing neutrinoless double {beta} decay offers the opportunity of determining the effective neutrino mass if the nuclear matrix element were known. Theoretical calculations are uncertain, and the occupation of valence orbits by nucleons active in the decay is likely to be important. The occupation of valence proton orbits in the ground states of {sup 76}Ge, a candidate for such decay, and {sup 76}Se, the corresponding daughter nucleus, is determined by precisely measuring cross sections for proton-removing transfer reactions. As in previous work on neutron occupation, we find that the Fermi surface for protons is much more diffuse than previously thought, and the occupancies of at least three orbits change significantly between the two 0{sup +} ground states.

Branching ratio Γ α / Γ γ of the 4.033 MeV 3 / 2 + state in 19 Ne

The branching ratio