D. Rendić

6He + α clustering in 10Be

In a kinematically complete measurement of the 7Li(7Li,α6He)4He reaction at Ei = 8 MeV it was observed that the 10Be excited states at 9.6 and 10.2 MeV decay by 6He emission. The state at 10.2 MeV may be a member of a rotational band based on the 6.18 MeV 0+ state.

Nucleon-nucleon quasi-free scattering in the p+d → p+p+n reaction at low bombarding energies

Abstract Proton-proton and proton-neutron quasi-free scattering (QFS) contributions in the p+d → p+p+n reaction have been measured for proton bombarding energies 4.5–13.0 MeV. The impulse approximation gives a good description of the measured spectral shapes for θ 1 = − θ 2 = 30°, and when normalized (with a factor ≈ 0.2 for p-p QFS and a factor ≈ 0.3 for n-p QFS) describes the peak cross-section energy dependence surprisingly well. The ratio of the peak cross sections ( σ np / σ pp ) exp is ≈ 2.0 for most of the bombarding energies, while the simple impulse approximation predicts ( σ np / σ pp ) imp ≈ 1.3. Coulomb effects are found not to be significant. The influence of the final-state interaction on the measured spectra has been discussed.

The (d, n) reaction on 1p shell nuclei at Ed = 11.8 MeV

Abstract The absolute differential cross sections have been measured for (d, n) reactions on 10, 11 B and 12, 13 C at an incident deuteron energy of 11.8 MeV. The measured angular distributions were compared with distorted-wave Born approximation (DWBA) calculations using average 1p shell parameters. These calculations successfully reproduce the general shape of the angular distributions, but fail to predict the magnitude of the cross sections at back angles. Absolute spectroscopic factors have been extracted and compared with theoretical predictions and previous experimental measurements. A definite J -dependence in the structure of the angular distributions is observed but is not reproduced by the DWBA calculations. The deduced spectroscopic factors are also compared with the results from (τ, d) reactions to look for a possible T -dependence.

Trace element concentrations in tree rings as indicators of environmental pollution

Abstract Proton induced X-ray emission spectroscopy has been successfully used to measure variations in relative and absolute trace element concentration levels in tree rings. Valuable information on past concentration levels, stored in the tree rings have been obtained. Peaks associated with 15 elements have been identified in all X-ray spectra. Variations of trace elements levels in the tree rings reflect the variations in their availability from the environment.

ANGULAR DISTRIBUTIONS OF QUASI-FREE SCATTERING CONTRIBUTIONS IN DEUTERON BREAK-UP BY PROTONS AND DEUTERONS.

Abstract Proton-proton and proton-neutron coincidence spectra from the p + d → p + P + n reaction were measured simultaneously for E p = 12.5 MeV and θ = θ 1 = − θ 2 in the interval 15° + = θ ≦ 60°. Deuteron-proton and deuteron-neutron coincidence spectra from the d + d → d + p + n reaction were measured also for E d = 12.5 MeV and θ = θ 1 = − θ 2 in the interval 15° ≦ θ ≦ 40°. Measured spectra are discussed in terms of the quasi-free scattering model. The shape of measured spectra and the angular dependence of the peak cross sections are fairly well reproduced. It was found that the ratio of the peak cross section for n-p and p-p quasi-free scattering in the p + d → p + p + n reaction varied from 1.3 at θ = 15° to 4.3 at θ = 42.5°. The ratio of the peak cross section for n-d and p-d quasi-free scattering in the d + d → d + p + n reaction was found to be constant and close to one. The variation of the σ np σ pp peak ratio in the p + d → p + p + n reaction can be attributed to the influence of n-p and p-p final-state interactions.

Neutron time-of-flight facility at rice university

Abstract A neutron time-of-flight facility in the T.W. Bonner Nuclear Laboratories at Rice University, developed in connection with the EN tandem Van de Graaff accelerator, is presented. The details of the pulse shape discrimination and neutron detection as well as the beam pulsing and bunching are described. Characteristic neutron detector efficiency data and neutron T-o-F spectra are shown.

On the observation of rescattering effects in the reaction 7Li(d, nα)4He

Abstract The reaction 7 Li(d, n α ) 4 He was studied at incident deuteron energies of 2.07 and 2.09 MeV in an attempt to observe n- α rescattering effects. Contrary to previous results no peaks were observed which could be attributed to rescattering.

Decay of 12C via the 11B(p, 2α)α reaction

Abstract The 11B(p, 2α)α reaction has been studied in a kinematically complete experiment over a wide range of angles at bombarding energies corresponding to resonances in 12C at Ex = 17.23 MeV, 17.77 MeV and 18.36 MeV. The coincidence spectra exhibit interference effects which can be reproduced theoretically if the identity of the three final-state particles is properly taken into account. A strong dependence of the cross section on the channel spin s and the angular momentum L in the 2α subsystem is demonstrated. Although no effort was made to produce best fits to the data, satisfactory overall agreement between theory and experiment could be obtained. The results of the calculations support the assignment Iπ = 3− for the resonance in 12C at Ex = 18.36 MeV.

Proton-proton quasi-free scattering in the p+d → p+p+n reaction for Ep = 4.5 − 13.0 MeV☆

Abstract Low-energy proton-proton quasi-free scattering was studied by coincidence detection of the two out-going protons at θ 1 = − θ 2 = 30° in the p+d → p+p+n reaction. The impulse approximation gives a good description of the measured spectral shapes and when normalized with a factor N = 0.2 describes the energy dependence of the peak cross section surprisingly well.

Final-state interactions in the 6Li(d; 6Li, p)n reaction

Abstract The 6 Li(d; 6 Li, p)n reaction has been investigated in a kinematically complete experiment at 10 MeV bombarding energy and at three pairs of angles. The spectra show pronounced 6 Li-n final-state interactions in the 9.7 MeV state and, especially in the 7.48 MeV state of 7 Li, in qualitative agreement with the known decay properties of these levels. At one angle, a possible indication of some contribution from the (isospin forbidden) 1 S 0 proton-neutron final-state interaction has been observed.