Table of contents

The role of multiple scattering corrections to the background scattering amplitude is discussed. The success of the Eguchi-Igi model (see Phys. Rev., vol.D8, p.1537 (1973)) in explaining the exotic peaks is analysed from the point of view of unitarity as incorporated in multiple scattering corrections.

Proton- gamma ray angular correlations and Doppler shifts have been measured in the ³⁹K( alpha ,p gamma ) reaction at E_alpha =14 and 15 MeV. Spin-parity assignments and lifetimes were obtained for the following levels: E_x=6140 keV, J^pi =6^-, tau =70_-20⁺³⁰ fs; E_x=4896 keV, J^pi =5^-, tau =64+or-30 fs; E_x=4353 keV, J^pi =4^-, tau =550+or-150 fs; E_x=4099 keV, tau =730_-110⁺¹⁴⁰ fs; E_x=4045 keV, tau =250+or-85 fs. A total of five enhanced E2 transitions has been observed from these levels. The results are interpreted in terms of collective models.

Negative parity states in ⁴²Ca have been excited with the ³⁹K( alpha ,p gamma )⁶²Ca reaction at bombarding energies of 9.5 MeV and 11.5 MeV. The lifetimes of the known negative parity states at 3953(4^-) keV. 4044(3^-) keV and 4099(5^-) keV were measured to be 4.7+or-0.3 ps, 240+or-70 fs and 580+or-145 fs respectively. Levels at 4353 keV and 4896 keV were shown to have J^pi of 4^- and 5^- with lifetimes of 760+or-100 fs and 80+or-30 fs respectively. Multipole mixing ratios were determined and several of the transitions were shown to have enhanced E2 strengths. The results are discussed in terms of the co-existence model of spherical and deformed states.

Amplitudes corresponding to K* and K** quantum-number exchanges in KN and pi N hypercharge-exchange scattering are obtained from data in the few GeV region using an analysis based on fixed -t analyticity in the form of fixed -t dispersion relations and finite energy sum rules. Comparisons are made with other amplitude analyses at 4 GeV/c, with some specific high-energy models, and with the results of a similar type of analysis out on K^+or-N charge-exchange scattering.

An attempt is made to explain the observed even parity spectrum and transition rates of ³⁶S. The calculation has been performed in two different ways. The first follows the shell-model approach while in the second the model space is expanded through the introduction of a limited number of deformed 6h-2p configurations. Both models produce energy spectra that agree with experiment. It is shown, however, that agreement with experiment on transition rates can be obtained only with the extended model.

The spin and parity of the 1924 keV level in ¹³¹I are determined uniquely by angular correlation measurement of the 1151 keV-774 keV cascade and conversion coefficient measurement of the 278 keV transition to be ¹¹/₂^-.

The K-capture to positron emission ratio (P_K/P_{beta +}) for the decay of ⁹¹Mo to the ground state of ⁹¹Nb has been measured and found to be about 9% lower than the theoretical value. This tends to agree with a recent review which indicated that experimental P_K/P_{beta +} ratios disagree with theory, particularly for high-Z nuclei.

Detailed analysis of phase-amplitude curves is found to provide much insight into the elastic scattering of heavy ions at intermediate and high energies, where numerical calculations become lengthy. The nuclear interaction is first treated by the strong absorption model, and a semiclassical analysis providing a link with Fresnel diffraction is found to have a very narrow range of validity. The nuclear interaction is then treated in the optical model.

The photodisintegration of ¹⁵N through excited states of the residual nuclei has been studied by measuring the yields of de-excitation gamma rays in a Ge(Li) detector. Cross sections for all observed transitions were deduced from measurements with bremsstrahlung end-point energies ranging from 15 to 35 MeV and account for an integrated cross section of 44 MeV mb. Bound states in ¹⁴N and ¹⁴C with a dominant (1p₁2/)^-1 or (1p₃2/)^-1 configuration are found to be strongly populated. The nature of the states in the ¹⁵N giant resonance is discussed. The ¹⁵N( gamma ,t)¹²C* (4.44 MeV) reaction was also observed and its integrated cross section is approximately 5% of the expected value of the E1 sum rule.

Measurements are presented for the mass and energy distributions of fragments from the fission of ²³⁵U and ²³⁸U, induced by electrons in the energy range 30-120 MeV. Solid state detectors were to detect the fragments. Both the mass and energy distributions suggest that the fission process has two distinct components. The change in the distributions for different electron energies indicate that the components are associated with different regions of excitation energy in the fissioning nucleus.

The authors compare measurements of charged/neutral hadrons in extensive air showers with calculations that include production of neutral kaons and nucleon-antinucleon pairs. At approximately 2*10⁵ GeV, observation and calculation agree; above approximately 3*10⁵ GeV, a different experiment appears to be significantly lower than calculation. If confirmed, the latter experiment will require a threshold in the nuclear physics around this energy.