The Excitation and Transport of Metal Vapour in Short Sparks in Air

The paper describes a study of the excitation temperature in certain spark discharges of accurately known current characteristics. The excitation temperatures are found by measuring intensity ratios for certain spectral lines where the relevant transition probabilities are known, and are comparable with earlier work by Ornstein and his collaborators on arc discharges. The excitation temperatures are, as would be expected, higher than those generally found for arc conditions. Certain peculiarities relating to the evaporation of electrode metal are described. In particular the presence of discontinuous evaporation was noticed, and it was found that different electrode metals showed considerable variations in their behaviour in this respect.