Table of contents

The interpretation of the observed partial correlation between the meson intensity at sea level and the barometric pressure, the other independent variables of the regression equation being the height of the 100 mb level and the stratospheric temperature, is discussed. It is shown that even though the decay effect due to changes in the height of the meson-producing layer is represented by a separate term in the regression equation, the barometer term does not represent a pure absorption effect but contains also a contribution from the μ-e decay. This decay contribution is due to the relativistic time dilation which makes the mean life of a μ-meson in the atmosphere depend on its energy loss and thereby causes its survival probability to change with changing sea-level pressure even if the height of the meson-producing layer remains constant. The decay effect is found to constitute about one third of the barometric effect observed in experiments performed at sea level. The simple total correlation between the meson intensity and the sea-level pressure is also discussed.

A rotational analysis has been made of the 1,0, 0,0, 0,1 and 1,2 bands of the A-X system and of the 1,0, 0,0 and 0,1 bands of the B-X system of InF. Two branches are found in the A-X bands, and three in the B-X bands, confirming the identification of A as ³Π₀₊ and B as ³Π₁. The internuclear distance in the ground state, r_e'' is 1.985 Å.

The mesomeric effect is discussed in terms of a mixing of the `locally excited' states of the hydrocarbon, and the `electron transfer' states. If the substituent behaves as an electron donor, the energies of the lowest electron transfer states can be estimated from the ionization potential of the substituent.

A substituent which has a small ionization potential will be expected to exert a strong mesomeric effect, since the electron transfer states have low energies. These states may give rise to new bands in the spectrum. The spectrum of aniline is discussed in these terms, and the band at 2350 Å is attributed to an excitation to an electron transfer state.

If the ionization potential is large, then, in general, there will be only a weak mesomeric effect. In this case it is only possible to estimate the change in energy of the lowest electronic states. A method is described whereby the inductive effect can be allowed for, and this is applied to find the mesomeric effect of a methyl substituent from the various methylated benzenes.

It is suggested that the long-range part of the Coulomb interaction of the electrons in solids can be treated by regarding the solid as a homogeneous dielectric. The theory is developed in a semi-classical way. It is found that there is a possibility of sustained electric oscillations in metals, and these are identified in the case of a free electron gas with the plasma oscillations of Bohm and Pines. The theory is used to discuss the plasma frequencies of metals and the energy loss spectra of fast electrons in Ruthemann and Lang type experiments. The connection with the optical properties is indicated.

A fairly general programme for the computation of atomic self-consistent fields without exchange has been prepared for the Manchester University electronic computer. Results obtained for the Zr⁴⁺ ion are given.

The cross section for direct inelastic scattering from the nuclear surface deformation is calculated and compared with the compound nucleus inelastic cross section. It is found, using optical model wave functions, that the direct process can be important in the regions of atomic weight near A = 150 and A = 240.

Polystyrene discs were irradiated in the scattered proton beam of the Birmingham synchrotron. The proton flux was found by counting tracks in a nuclear emulsion exposed near the polystyrene disc. From the observed activity of the discs the cross section for the production of 20.5 minute ¹¹C from carbon by 950 MeV protons was found to be 20.5 ± 1.1 mbn. The variation of cross section over the energy range 200-950 MeV was also studied.

Using a triple ionization chamber to collimate and record recoil protons from a hydrogenous radiator, angular distribution measurements have been carried out on a number of neutron groups emitted as a result of the bombard by 9MeV deuterons of targets of sodium carbonate, aluminium and phosphorus. Spins and parities of the resulting states of the 4n nuclei ²⁴Mg, ²⁸Si and ³²S have been assigned by applying the theory of the stripping process. In the case of ²⁸Si, the first T = 1 level is identified and its characteristics compared with those of the ground state of ²⁸Al.

A description is given of a new fast-neutron spectrometer which utilizes scintillation counters and which has a relatively high efficiency of detection. The instrument is suitable for use at neutron energies of 4 MeV and above and has been used to investigate the stripping reaction ¹⁹F(d, n)²⁰Ne. The angular distribution of four neutron groups has been found and the theory of the deuteron stripping process has been applied to analyse the results and to obtain information about the corresponding levels in ²⁰Ne.

The theory of the Hall effect at high frequencies is developed in terms of the `surface Hall coefficient' defined in a similar manner to the complex surface impedance for metals. Calculations of this coefficient have been carried through for a metal with two overlapping energy bands, and the variations with frequency and with field strength are shown graphically for certain special cases.

At very low frequencies the Hall coefficient is constant at the d.c. value; at higher frequencies it increases as the square root of the frequency and ultimately in the infra-red region for normal metals, attains a limiting value independent of frequency. Furthermore a phase difference exists in general between the Hall field and the specimen current but this decreases to zero at very low and very high frequencies.

The beta-decay spectrum from the ground state of ²⁶Al has been observed by means of a scintillation spectrometer. It has an end point of 1.17±0.05 MeV and corresponds to a second forbidden transition, ΔJ = 3, no. The beta decay is followed by a gamma ray of energy 1.76±0.1 MeV.

The nuclear reactions (n, n'), (p, p'), (n,p) and (p,n) are considered to take place by the direct collision of nucleons at the surface of the target nucleus. The angular distribution of any γ-rays following these reactions is considered, and two simple cases presented explicitly.

Simple formulae are given for the polarization effects, in nuclear reactions, of spin ½ particles and photons, and applied to elastic scattering by a potential well with spin-orbit coupling.

A description is given of a cloud chamber experiment in which is investigated the dependence of the multiple and large-angle scattering of μ-mesons on momentum, sign and atomic number. The results are compared with Molière's theory for a point nucleus, Olbert's theory for an extended nucleus, and a more accurate modification of Olbert's theory. These theories give an adequate description of the multiple scattering for small momentum transfers. For large momentum transfers, where the size and structure of the nucleus should profoundly modify the scattering, Molière's theory is found to give a better description than Olbert's theory.

Calculations are made of the magnetostriction constants λ₁₀₀ and λ₁₁₁ for nickel at 0°K, based on the collective electron model and the calculations of the author of the N(E) curve for the 3d electrons in that metal. The values − 187 × 10^-6 and − 44 ×10^-6 obtained for λ₁₀₀ and λ₁₁₁ respectively are both rather larger than the latest experimental figures which, however, are available only at 120°K. The method of calculation is very similar to that used by the author previous work on ferromagnetic anisotropy and the possible reasons for discrepancy between theory and experiment are also similar.

Corrections to 1955 Proc. Phys. Soc. A 68 905.

Corrections to 1955 Proc. Phys. Soc. A 68 910.