On the reflection and re-emission of electrons from metal surfaces: and a method of measuring the ionizing potential of such surfaces

In making photo-electric measurements upon suspended droplets of mercury, one of us has repeatedly found that photo-electrons are always released when the droplet is illuminated by the ultraviolet line of wavelength 2536 Angstroms. On the other hand, it has been frequently proved that the molecules of mercury vapor are not ionized at all by these wave-lengths. The quantum of energy, then, which must be incident upon mercury in the liquid form in order to detach electrons from it is quite different from that required to detach electrons from the free atoms. It is to be expected from this fact that the "ionizing potential" also of liquid mercury will be quite different from that of the same element in the gaseous form. A considerable group of investigations has accordingly been begun in the Ryerson Laboratory for the purpose of determining, in the best vacua obtainable with modern means, the effect of surface conditions upon the emission of electrons from solids and liquids. Preliminary results from one of these investigations are reported herewith.