Table of contents

Mono-energetic neutrons have been used to produce recoil protons, deuterons and α-particles in a proportional counter The maximum pulse sizes produced by the different recoil particles are compared with the accurately known ratios of maximum recoil energies From the results for protons and deuterons it can be inferred that, for protons between 200 and 550 keV energy, the ionization is proportional to the energy with a deviation of less than 1% The total ionization in argon produced by a proton is about 8% greater than that of an α-particle of equal energy, for energies between 200 and 400 keV.

The increase with temperature of the total cross section of iron for very slow neutrons has been measured with the help of a cyclotron and a neutron velocity selector. Part at least of this increase is caused by the inelastic scattering associated with lattice vibrations, but the observed rise in cross section is much greater than is predicted by the theory of this effect. It is suggested that a ferromagnetic scattering process may be responsible for the discrepancy

The theory of the mean square angle of emission of nucleons resulting from a high energy nucleon-nucleus collision is developed Graphical results are given both for light and for heavy nuclei

The hyperfine structure of the 6s and 7s levels of Au I have been measured. The values of the nuclear magnetic moments calculated from the structure of these two levels using the Goudsmit-Fermi-Segrè formula agree Since the Fermi-Segrè factor is very large (1.424) for the 6s level and small (1.038) for the 7s level, this affords a good check on the validity of the method introduced by Crawford and Schawlow for the evaluation of this factor. When the corrections for the finite size of the nucleus are included, the spectroscopic value of the nuclear magnetic moment of ¹⁹⁷Au is +0.136 n m

Irradiation of holmium with pile neutrons produces, in addition to 27-hour ¹⁶⁶Ho, a new long-lived holmium isotope with a half-life greater than 30 years. It is shown that it cannot be ¹⁶⁷Ho produced by neutron capture in ¹⁶⁶Ho, nor ¹⁶⁴Ho produced by a (n, 2n) reaction. It is therefore probably an isomer of the 27-hour ¹⁶⁶Ho.

It decays with emission of β-particle groups of energies 0.18, 0.28 and 1.1 MeV, γ-rays of energies 0.830, 0.725, 0.280, 0.212 and (weak) 0.095 MeV, and weak erbium K x-rays.

β-γ and γ-γ coincidence measurements have been made and a decay scheme suggested

The form of the structure function of extensive showers at small distances from the core has been investigated by observations of coincidences between ionization chambers at sea level

The observations considered are the decoherence curve and the burst-ratio distribution. Both sets of results indicate a structure function that varies as 1/r^0.8 for small r (less than 0.04 lateral shower units at sea level) as opposed to the well-known Moliere function which behaves as 1/r for small r. A modified structure function is given in tabular form. The advantages of the burst-ratio distribution method of studying the structure function are discussed.

Previous work on far ultra-violet atomic absorption spectra is summarized and discussed with particular regard to the phenomenon of auto-ionization. Details are given of a current programme of work on line and band absorption spectra of vaporized elements and hydrides, in which special attention is paid to the vacuum ultra-violet. Results for the Schumann region absorption spectrum of Ga vapour are given.

The ultra-violet absorption spectra of GeSe and GeTe have been obtained. New band-systems of both molecules have been found, and the vibrational analysis of one of them, the E-X system of GeSe, has been completed. The corresponding system, E-X, of GeS has been considerably extended, and fairly sharp dissociation limits have been found for both GeS and GeSe. A satisfactory spectrogram of GeO in absorption has been obtained. Values of the electronic and vibrational constants for all the known states of the four molecules are derived.