Table of contents

The ground state beta transition of ¹⁴⁴Pr has been studied experimentally and the results analysed. The analysis depends upon the spin assumed for the ground state of ¹⁴⁴Pr; if that state has spin and parity 0^-, as strong evidence indicates, then pseudoscalar interaction is needed to explain the results satisfactorily. The ratio of the coupling constants of pseudoscalar to tensor interactions required is approximately 100.

An investigation has been made of π⁺-p scattering at incident pion energies of 20(⁺¹⁵_-10) MeV, using a hydrogen filled diffusion cloud chamber in a magnetic field. Fifteen π⁺-p scattering events were observed and the incident pion spectrum and path length were determined from measurements on π-μ decays. The results were analysed by using the values for the phase shifts α₃₃ = 0.235η³, α₃₁ = 0 and assuming that α₃ is directly proportional to η. The phase shift α₃ was then found to be -(0.13 ± 0.035)η radians, where η is the pion momentum in mass units.

The integral shower density spectrum from 20-1000 particles per square metre is measured with three-fold proportional counters 60 metres above sea level, and follows a law ν(ρ) = 540 ρ^{-1 39±0.04} h^-1, for ρ < 500 particles m^-2, in agreement with previous Geiger counter results; an agreement which confirms energy loss measurements as a means of particle density determination. For ρ > 500 the exponent increases quickly, reaching 2.2 at ρ = 1000, which is typical of the value observed with ionization chambers.

The density spectrum is analysed, allowing for effects of shower age on structure to obtain the distribution in number S(N) = 2.3 × 10^-4 (N × 10^-6)^{-1 47±0 1} m^-2 h^-1, with evidence for a rapid increase in exponent above N = 10⁶ particles. Using cascade theory the latter is shown to be produced by a primary energy spectrum V(E) = 0.32 (E × 10^-14)^{-1 5} m^-2 h^-1 sterad^-1, for 10¹³ < E < 10¹⁵, above which the exponent increases rapidly, reaching about -3 at E = 10¹⁷ eV. Since shower primaries of these energies should be little affected by solar or terrestrial magnetic fields, this will be the form of the primary spectrum.

A simple perturbation method is suggested for the calculation of energies of the states of homonuclear molecules at large internuclear distances R for which the identity of the nuclear fields must be taken into account, a comparison with exact data on the 1sσ_g and 2pσ_u states of H₂⁺ showing that results of high accuracy can be obtained without undue labour. The method is also applied to the ¹Σ_g and ³Σ_u states of H₂ and reasons are advanced for supposing that the results are, at least for R greater than 4a₀, more accurate than those of any previous calculation.

The reaction ¹³C(α, n)¹⁶O has been examined from 1.0 to 2.5 MeV bombarding energy. The positions and widths of seven resonances have been measured. Angular distributions have been obtained in five cases, and some tentative spin and parity assignments made. Measurements of the absolute cross section are given and values of reduced neutron and alpha-particle widths have been calculated for three levels in ¹⁷O.

Electron-sensitive nuclear emulsion impregnated with RaD citrate was used. RaD events associated with β-particles of RaE were studied to determine the total number of developed grains produced in each RaD event. An analysis of the resulting grain-count distribution provides evidence of the occurrence of a ground-state to ground-state β-process in RaD with an intensity of 15.5 ± 3.5% of all disintegrations. The total intensity of excitation of the 46.5 keV state of RaE is thus 84.5 ± 3.5% and the intensity of conversion electrons from this state is 81 ± 4%. The last of these values is consistent with the results previously published by Wu, Boehm and Nagel and by Cranberg.

A liquid scintillator, designed to detect stars produced in the phosphor by the cosmic radiation at sea level, has been used to investigate the star transition curve at depths of lead absorber in the region of twenty centimetres. The anomalous maximum at a depth of twenty centimetres, first reported by Schopper, Hocker and Rossle, has been confirmed. It appears that low energy μ-mesons are the most likely primaries, the stars being produced by neutrons released in the slow μ-meson nuclear absorption process.

A measurement has been made of the ratio of the numbers of neutrons emitted in directions parallel and perpendicular to the motion of the fission fragments, when fission is induced in natural uranium by 147 MeV protons. The value obtained, 1.27±0.11, is consistent with the greater part of the neutron emission occurring before fission, the remainder (2.5 ± 1 neutrons) being emitted from the moving fragments, as in thermal fission.