Table of contents

The cross section for the ²H(d,n)³He reaction at energies relevant to fusion reactors is calculated within an approximate antisymmetrised one-step reaction model. Nuclear wavefunctions consistent with a realistic nucleon-nucleon interaction are used throughout. In marked contrast with previously reported approximate calculations of this type, which claim agreement with data, the authors find the data to be overestimated by two orders of magnitude for centre-of-mass energies of order 55 keV.

Tidal symmetry is a recently proposed concept which introduces considerable simplifications into the theoretical analysis of heavy-ion scattering and fusion. It also facilitates the understanding of features of nuclear reactions induced by polarised heavy ions. Key pointers to this symmetry are presented and compared with new experimental results and published data for ⁷Li elastic scattering. The discussion gives an indication of the usefulness of the tidal symmetry concept.

A change of the M1 transition probabilities is observed in the band crossing region in the positive-parity yrast band of ⁷⁹Kr. This change is compared with that observed in the neighbouring nucleus ⁸¹Kr and is interpreted on the basis of a semiclassical coupling scheme of particle angular momenta.

It is shown that the spectrum of dipole radiation of the charge-dyon bound system described by both the Schrodinger and Pauli equations contains direct information on the spatial parity violation in electrodynamics with magnetic charge. The corresponding matrix elements are calculated.

The author has pinpointed some crucial differences between the observations made at the CERN pp collider at S¹2/=540 GeV and pp reactions in the ISR range of energies and has tried to analyse them in the light of a version of the sequential chain model. The conclusion is that all these differences are not simply the result of the difference of one order of magnitude in the CM energy between the two sets of experiments but, more importantly, due to other reasons connected with the constituent picture of hadrons and the consequent multiparticle dynamics as a whole.

In the framework of a chiral-invariant effective Lagrangian theory, the authors have discussed the propagation of a pion through an infinite nuclear medium with special emphasis on the role of the Delta (1232). In particular, the full spin-³/₂ projector operator and the most general form of the pi N Delta interaction have been used in order to evaluate the Delta contribution to the pion self-energy. On the basis of an investigation into this problem, they confirm certain a priori assumptions regarding the effects of Delta (1232), which are seen very often in the literature. However, some of the results are at variance with the usual forms for the calculation of the Delta contribution to the pion-nucleus interaction, reflecting the fact that the off-mass-shell effects of the Delta (1232) are appreciable.

A simple, effective nucleon-nucleon interaction for shell-model calculations in the sd shell is derived from the Reid soft-core potential folded with two-body correlation functions which take account of the strong short-range repulsion and large tensor component in the Reid force. The interaction is in astonishing agreement with the fitted potentials of Preedom-Wildenthal (1972) and Chung-Wildenthal (1979) in the lower half of the sd shell and with Chung-Wildenthal in the upper half of the sd shell. The mass dependence of the interaction is compared with that postulated by Wildenthal (1984). The authors conclude that most of the mass dependence resides in the diagonal matrix elements.

A model is presented for calculating the Coulomb contribution to shell-model binding energies, for an arbitrary model space. The method is appropriate for both ground and excited states. The parameters of the model are determined by a fit to measured Coulomb displacement energies. As an example, Coulomb energies are computed for nuclei around mass 40.

The analysing power A_y( theta ) for ¹²C(n,n)¹²C elastic scattering and for inelastic scattering to the first excited state (J^pi =2⁺, Q=-4.44 MeV) of ¹²C was measured at 18.2 MeV. A pulsed polarised neutron beam was produced via the ²H(d,n)³He polarisation transfer reaction. The A_y data, together with published cross sections, were analysed in the framework of the spherical optical model and in the coupled-channels formalism. A phase-shift analysis at 18.2 MeV gives supporting evidence for a broad ⁵/₂⁺ resonance. The ¹²C recoil kerma factors and values for the n+¹²C reaction cross section were deduced and compared with previous estimates and predictions.

The g factors of the 2₁⁺ states in ^84,86,88Sr have been deduced using the thin-foil transient field technique with the field calibration of the Rutgers group. The values are g(⁸⁴SDR)=+0.419(47), g(⁸⁶Sr)=+0.273(50) and g(⁸⁸Sr)=+1.15(17). The mean lifetimes of the 2₁⁺ states in ^86,88Sr were determined by the Doppler shift attenuation method to be 2.10(22) ps and 0.219(23) ps respectively. The g factor and lifetime results are compared with shell model and interacting boson model predictions.

14 MeV cross sections for the reactions ¹⁰⁷Ag(n,2n)^106m,gAg, ¹⁰⁹Ag(n,2n)^108gAg, ¹⁰⁹Ag(n,p)^109m+gPd and ¹⁰⁹Ag(n, alpha )^106mRh were measured relative to the ⁵⁶Fe(n,p)⁵⁶Mn reaction employing the activation technique. Both beta and gamma counting were used as appropriate. Accuracies of between 2 and 5% were achieved for the (n,2n) reactions, 5% for the (n,p) reaction and 10% for the (n, alpha ) reaction. The isomeric cross section ratio was measured for the ¹⁰⁷Ag(n,2n) reactions.

Measurements of the internal conversion electron spectrum and the identification of EO transitions linking the excited O⁺ states in ¹⁷²Yb provide new information on the level structure of this nucleus. The (n,e^-) reaction with a Yb₂O₃ target enriched in ¹⁷¹Yb was used and all possible EO transitions were searched for. Several new low-energy EO transitions were observed and evidence was found for a new 0⁺ level at 1920 keV. This may be due to pair excitation, which is also a possible explanation for the 1405 keV 0⁺ level. The authors show that an alternative explanation for the 1405 keV level is that it is the head of a K^pi =0⁺ mixed symmetry band with band members at 1477 keV (2⁺) and 1633 keV (4⁺). The level energies, B(E2) values, multipole mixing ratios and X values are compared with the predictions of the DDM and the IBA-2.

Presents new results of an analysis of the lateral distribution of electrons in extensive air showers. It is shown from experimental data that the lateral distribution of electrons is steeper than the NKG function but not as steep as the function proposed by Lagutin et al. (1979). The author also deduces from the experimental measurements a structure function which yields an age parameter which is consistent with the longitudinal stage of shower development.