Table of contents

A semi-empirical method inspired by Blomqvist's (1969) previous calculations of the excitation energy of the lowest 9/2^- state of ²⁰¹Tl is applied to similar calculations in different Tl, Au and Ir isotopes. These semi-empirical estimates agree well with the experimental values of the excitation energies as well as with the energy differences deduced from the analysis of the total potential energy surfaces calculated microscopically with Nilsson's model. The same excitation energies are computed with a spherical HF-BCS model which does not reproduce the available experimental data so well. An interpretation of these deviations is attempted.

The fragmentation of the nuclear system ²³⁸U-²³⁸U is studied quantum-mechanically within the fragmentation theory. Mass distributions are obtained by solving the time-dependent Schrodinger equation which depends on the fragmentation coordinate and on the classical trajectories of the relative motion of the colliding ²³⁸U nuclei. The mass transfer leading to the formation of superheavy elements is predicted.

Owing to weak interactions, the three-photon vertex is non-zero. From gauge invariance and symmetry requirements, it is shown that the C=-1P=-1 vertex amplitudes are at least of order q⁷ in the limit of soft photon momentum q and that if any two photons are placed on mass shell the form factors vanish identically. To lowest order in q the effective current is in fact given by j_rho =b epsilon _{kappa lambda mu nu} ( delta ²(F^{kappa lambda} delta _rho F^{mu nu} )- delta _rho (F^{kappa lambda} delta ²F^{mu nu} )). b is estimated in certain models of weak interactions.

The dispersion relation method, together with the conformal mapping technique, is used to estimate the real part of the forward p-⁴He elastic scattering amplitude in the proton laboratory energy range 1.5-10 GeV. The predictions obtained rest heavily on the phase-shift input and need testing by direct measurements of the real parts in experiments performed in the Coulomb interference region.

The approximate method proposed by Butler et al. (1970) for the solution of the Bethe-Goldstone equation in finite nuclei is shown to be a very useful method for obtaining wavefunctions with short-range correlations for further application in nuclear physics calculations. As an example, parity mixing in ¹⁹F is calculated and the approximate calculation is indeed a very good approximation to earlier exact calculations.

The gamma rays emitted in the decay of 6.2 h ¹²⁷Cs to levels in ¹²⁷Xe have been studied in singles and coincidence with Ge(Li) detectors. A decay scheme for ¹²⁷Cs has been constructed on the basis of the results of these measurements. The resulting level scheme for ¹²⁷Xe is discussed in the light of present knowledge of the level schemes of the other odd-mass Xe nuclei and the results of nuclear model calculations.

Measurements of the electromagnetic lifetimes of the first four excited states of ¹⁹²Pt have been made by the self-comparison method using electron-electron coincidences. The partial lifetimes of the gamma transitions involved have been interpreted in terms of the pairing-plus-quadrupole model of Kumar and Baranger (1968).

Angular distributions have been measured for the elastic and inelastic scattering of protons from magnesium isotopes at the proton energy E_p=9.1 MeV. Optical-model parameter searches yielded potential parameters used in the total Hauser-Feshbach and DWBA calculations. The ratios of the total experimental to the total Hauser-Feshbach inelastic cross sections for different states of ²⁵Mg and ²⁶Mg are found to lie in relatively narrow bands around the average values. A significant enhancement of these ratios with respect to the average values is observed only for the first excited members of the ground-state rotational bands of these nuclei. The enhancement is attributed to direct rotational excitation. The deformation parameters for these states are extracted with the aid of DWBA and are compared with those previously established.

The alpha - alpha coincidence spectra from the ⁷Li(d, alpha alpha )n reaction were used to determine the excitation energy and width of the first excited state of ⁵He. The results obtained were E_x=4.1+or-0.2 MeV, Gamma =4.4+or-0.2 MeV.

The problem of the calibration of detectors used in extensive air shower experiments is discussed. A method using light-emitting diodes to provide the necessary calibration for large-area scintillation counters is described. The results of applying this method of calibration to the Sydney air shower array are presented, showing two possible sources of error in the scintillation detectors.

The upper end of the cosmic ray energy spectrum is re-assessed using data obtained from the Sydney giant air shower recorder. The effects of after-pulsing are incorporated into the interpretation, giving rise to a spectrum somewhat steeper than previously published. It is found that the resulting differential slope of -3.35+or-0.15 is close to the steepest of other experiments, agreeing well with the values of Haverah Park and Mount Chacaltaya.