Table of contents

A comparison of the pattern of level energies of the ground state bands in even-even Cd and Te nuclei indicates that in Te nuclei for which proton and neutron orbits belong to the same major shell (50 to 82), pronounced neutron-proton interaction occurs. This explains the large h_11/2 admixture to the proton configuration of the neutron rich Te isotopes underlying the negative quadrupole moments commented on by Hall and Thomas.

The excited states of ¹⁵⁹Tb have been studied in the reaction ¹⁶⁰Gd(p,2n gamma )¹⁵⁹Tb using in-beam gamma ray spectroscopy. New levels of two strongly mixed negative-parity bands and of the known K^pi =¹/₂⁺ band have been identified. From an analysis of the E1 transitions de-exciting the ⁷/₂⁺(404) level to the coupled ⁷/₂^- states, the mixing between them was evaluated to be 17%. In order to explain the experimental value of the decoupling parameter for the ¹/₂⁺ band, an influence of the ¹/₂⁺(660) configuration is suggested.

The measured strengths of excitation in the (n, gamma ) and (d,p) reactions on the N=82 nuclei ¹³⁸Ba, ¹⁴⁰Ce and ¹⁴²Nd are compared and it is found that they are strongly correlated for ¹³⁸Ba and ¹⁴⁰Ce but not for ¹⁴²Nd. The results for ¹³⁸Ba and ¹⁴⁰Ce may be explained in terms of the common unique parent assumption of Lane and Wilkinson. This suggests the predominance of direct capture in the thermal neutron cross section for these nuclei, whereas the ¹⁴²Nd cross section is thought to be largely due to compound nucleus formation as is the general rule.

Simple theories of interacting classical relativistic massive spin-1 and spin-³/₂ fields are studied. In these examples, it is found that if a theory is acausal in the sense of Velo and Zwanziger, it is also not Lorentz covariant. The breakdown of Lorentz covariance is seen to manifest itself in the constraints, which must be satisfied by the interacting fields, not determining all the dependent fields components simultaneously in all inertial frames of reference. Some remarks on the present state of massive spin-³/₂ theories are made.

It is suggested that various channel cross sections for K^-p interactions strongly exhibit their different duality properties in the resonance region as well as at high energies. In particular, it is argued that non-diffractive processes with no (u,t) dual amplitude are resonance dominated in the real part as well as the imaginary part. Thus, from a bootstrap point of view, the (u,t) amplitude should be considered the driving force behind the (s,t) and (s,u) amplitudes and reciprocally.

The dual absorptive model is applied to pi N backward scattering in detail and through the fits to the available data, the N(I_u=¹/₂) and Delta (I_u=³/₂) exchange amplitudes are studied. The interaction radius R and the slope parameter B for the N amplitudes are found to be consistent with those of the forward scattering, while the slope parameter B for the Delta amplitude is found to be rather large. This inconsistency is attributed to the incorrect form of the Re Delta as given by the model. Possible mechanisms to produce the correct Re Delta are given.

The 4.510 MeV level in ²⁷Al has been conclusively shown to have a J^pi assignment of ¹¹/₂⁺. The branching ratio was measured to be 77+or-2% to the 2.211 MeV ⁷/₂⁺ state and 23+or-2% to the 3.004 MeV ⁹/₂⁺ state, the multipole mixing ratio for the latter transition being -1.16+or-0.11. It is suggested that the 4.510 MeV ¹¹/₂⁺ and the 3.004 MeV ⁹/₂⁺ levels are possibly members of K^pi =¹¹/₂⁺ and K^pi =⁹/₂⁺ bands respectively obtained by coupling an Omega =¹/₂ (Nilsson orbit 9) neutron to the 5⁺ ground-state configuration of ²⁶Al.

States in ⁷⁸Kr have been excited by the decay of ⁷⁸Rb and by the reaction ⁶⁸Zn(¹²C,2n) and a level scheme has been built up from the observed gamma -ray spectra. The presence of a number of states, previously reported, has been confirmed and four new levels at 2572.5, 2900.2, 3160.7 and 3723.8 MeV are identified. Firm spin and parity assignments are made for states at 1016.9 MeV (0⁺) and 1147.5 MeV (2⁺) and tentative assignments for states at 1564.4 MeV (3⁺) and 1872.5 MeV (3⁺,4⁺).

The general form of the final state distribution is given for inner bremsstrahlung by the electron pair produced in 0-0 nuclear transitions with no parity change. The expression for the resultant photon energy spectrum is given and evaluated numerically for the transition in ¹⁶O.

The number of L X-rays of lead emitted per alpha disintegration of ²¹⁰Po has been measured, in terms of the known emission of neptunium L X-rays by ²⁴¹Am, using a thin Ge(Li) X-ray detector, a low geometry alpha particle counter and a weak ( approximately 4 mu Ci) source of ²¹⁰Po. The result, (1.41+or-0.12)*10^-4L X-rays per alpha , is substantially lower than the results of previous measurements but is still in marked disagreement with the predictions of calculations based on the theoretical approach of Migdal. The result is in fair agreement with a recent calculation, using a special formulation of the binary encounter approximation, by Hansen. Previous theoretical and experimental work is reviewed and the results of a simple calculation of the L shell ionization probability, using the sudden approximation are given.

Angular distributions for the ¹⁶O(³He, alpha )¹⁵O reaction induced by 15 MeV ³He particles have been measured. Distributions characterized by single-nucleon pickup have been compared with the local zero range form of the DWBA. A normalization factor of 14.2 has been estimated and absolute spectroscopic factors have been extracted for excited states in ¹⁵O up to 10 MeV. A discussion for the odd and even parity states has been given in the weak-coupling model. Neutron filling probabilities for the 1d_5/2-2s_1/2 and 1d_3/2 orbits have been calculated for the ¹⁶O ground state.

A strong correlation has been observed between the 0 degrees and 180 degrees excitation functions for the ¹²C(¹⁶O, alpha )²⁴Mg reaction leading to the 13.2 MeV 8⁺ level. The possibility that this is due to exciting intermediate structure peaks at E_cm=13.7, 14.7, 16.0 and 18.0 MeV, is considered. It is concluded that the reaction most probably excites a narrow resonance ( Gamma approximately=70 keV) with J^pi =9^- or 10⁺ at E_cm=13.7 MeV. Weak evidence supporting the existence of anomalies at E_cm=16.0 and 14.7 MeV is presented. The possibility that the reaction excites a band of quasi-molecular states is discussed. An alternative explanation of the strong correlation in the data, based on the assumption that the reaction proceeds preferentially through either even or odd angular momentum states, is also considered.

The time sequence of detection of Cerenkov light in the deep-water detectors used at Haverah Park is used to establish a shower parameter insensitive to the total energy of the primary particles but yielding a measure of fluctuations of development among showers. Values of departure of individual showers from the mean behaviour now established are most reasily understood if some of the primary particles of energy E_p approximately 10¹⁸ eV are light, probably protons but perhaps alpha particles.

Recent direct experimental measurements of the primary proton spectrum have given a power law with differential slope gamma _d approximately -2.75 for energy less than about 10¹² eV. Extrapolation of this spectrum gives intensities of the order of those derived from extensive air showers in the region of 10¹⁸-10¹⁹ eV. The data from a variety of experiments which had previously indicated intensities significantly above this spectrum, particularly in the range 10¹⁴-10¹⁶ eV, are re-examined critically. It is concluded that the intensities are indeed higher and that a single exponent is quite inadequate to describe the spectral range 10¹⁰-10²⁰ eV.

The production spectrum of charged pions and the primary cosmic ray nucleon spectrum have been derived from the experimental muon spectrum determined near the geomagnetic equator at the zenith angles 45 degrees W and 60 degrees W. The derived pion spectrum follows the relation P(E_pi )dE_pi =(0.22+or-0.03)E_pi ^{-(2.65+or-0.12)} dE_pi and the primary spectrum agrees with the relation N(E_p) dE_p=2.9E_p^-2.65 dE_p. The results have been compared with the values expected from the vertical muon spectrum.

An apparatus employing twin telescopes to study the azimuthal variation of cosmic ray muon intensity was operated at Ahmedabad (geographic 23 degrees N, 37 degrees E; geomagnetic latitude 14 degrees N). Fourteen directions were scanned for long time intervals to give a counting rate accuracy of about 0.4% for each direction. Experimental results are presented. Variation in the coupling constant values in the rigidity range 12-26 GV is rather flat. Some implications of this behaviour are discussed. A theoretical method is described for the estimation of coupling constants applicable to muon telescopes. Correction for the fact that alpha particles and heavy particles have a cut-off (in terms of momentum per nucleon) at half the value for protons is incorporated in the calculation. The method is verified by comparing the theoretical results with experimental data on the latitude effect (namely, for zenith direction) and on the azimuth effect for fixed zenith angles. Theoretically estimated coupling constants for different zenith angles and different atmospheric depths are presented.