Table of contents

Ammonia-oxygen, ethylene-oxygen and other diffusion flames were examined spectroscopically using the flat flame technique described in a previous paper. Each flame is shown to consist of a main reaction zone where the temperature is a maximum. The emission from this zone is thermal, and the component gases are in chemical equilibrium. On either side of the main reaction zone there is a region with a steep temperature gradient which constitutes a pre-heating zone Fuels such as hydrocarbons or ammonia and oxidizers such as nitric oxide undergo chemical change in these pre-heating zones. On the fuel side the change is principally a thermal decomposition because the main reaction zone presents a barrier to oxygen penetration Thus carbon formation in hydrocarbon diffusion flames is essentially a pyrolytic process. The application and value of absorption spectroscopy are discussed and quantitative measurements of the concentrations of molecular oxygen and OH radicals are recorded which could not have been otherwise obtained. These results and a number of qualitative observations clearly show that diffusion flames with oxygen at atmospheric pressure have the structure predicted for a flame in which diffusion is the rate determining process A number of differences are described between the characteristics of diffusion and pre-mixed gas or Bunsen flames

Processes of electrónic excitation in flames are briefly discussed, and it is shown that if there is lack of equilibrium the reversal temperature may be closer to the effective vibrational temperature of the surrounding molecules than to the mean translational temperature. The lack of radiative equilibrium in all flames will cause measured temperatures to be too low; for a flame with air at 2000° k using Na the error will be between 3.3° and 1.6° at 1 atm. and more at lower pressure For hot flames, above 2700° k, the OH band may be used for reversal measurements; it appears to give satisfactory results and has some advantages over the use of sodium.

A general process, by which light can be absorbed in insulators at frequencies less than the frequency corresponding to the energy gap, is considered. Using an Einstein model with a constant energy gap, calculation of such a process is made by means of the method of intermediate states. The results are tested for the case of cadmium sulphide, and agreement with experimental results is found to be good when allowance is made for mathematical approximations made in the calculations.

Layers of silver and thallium halides have been evaporated, in vacuo, on to cleavage surfaces of rocksalt, potassium bromide, magnesium oxide and mica, at various substrate temperatures. These layers have been studied by means of electron diffraction. Examples of both high and low inter-atomic misfits between the substrate and the oriented overgrowth are found. In the case of silver chloride on potassium bromide, a chemical reaction occurred between the substrate and the deposit. Thallium chloride crystallized in an abnormal rocksalt type structure on potassium bromide, but had its normal caesium chloride type structure on the other substrates used.

General relations are derived between Pockel's elasto-optical constants and the polarizability derivatives α_ρσ,μ ( l, kk' ) used in Born's theory of the Raman effect in crystals. Numerical data are given for the case of diamond. Using these relations a formula is derived for the intensity of the Brillouin components of crystals in terms of the elasto-optical constants. This formula avoids the simplifications implied in an earlier expression due to Leontowitsch and Mandelstamm.

A theoretical investigation is made of the amount by which a dissolved gas should reduce the tensile strength of a liquid. The tensile strength is assumed proportional to the surface energy of a vapour nucleus, which is further assumed to have the form of a product of a function of its radius and a function of the dissolved gas concentration. The surface tension of a one-component system is expressed in terms of the van der Waals constants (developing Fowler's theory) and the treatment is extended to a two-component system on the basis of Wall and Stent's theory of van der Waals binary mixtures. The conclusion is reached that the reduction in the tensile strength of water caused by saturating it with air at a pressure of one atmosphere is less than ½%.

By extending Green's treatment of the classical virial theorem, a formula for the bulk modulus of an assembly of atoms, when classical physics applies, is derived. This formula involves the binary and ternary distribution functions.

By measuring the energy of photo-protons from deuterium the X-ray spectrum of a betatron, of maximum energy 20 MeV, has been deduced. A small difference between the experimental determination and the theoretical curve in the 10 MeV region is found.

Some measurements on the angular distribution of thin target radiation produced in a synchrotron are reported using ionization chambers to measure the x-ray intensity. Quantitative agreement has been obtained with the bremsstrahlung-multiple scattering theories of Schiff and Lawson for the case of a platinum target in the range of electron energies of 10-14 MeV.

The deuteron beam from the Liverpool 37 in. cyclotron was used to bombard a thin beryllium foil in a vacuum chamber The photographic plate method was employed in detecting the charged particles emitted from the reaction. The angular distribution of the elastically scattered deuterons shows a secondary maximum at 65°. Angular distributions of the two longest range proton groups are compared with the recent theories of the angular distributions of the (d, p) and (d, n) reactions. The results indicate that both ground state and first excited state of the residual nucleus ¹⁰Be have even parity and spin either 0, 1, 2 or 3.