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Production of Positron and Electron Pairs by Bombardment of Mercury with β-Particles of Low Energy


SKOBELZYN and Stepanowa1 have reported the production of positrons when β-particles of energy 1–3 MV. impinge on solid lead. In order to conserve electric charge, the phenomenon rmist have involved the production of a pair of positive and negative electrons. Examination of about a thousand photographs of the tracks of β-particles from radium E in a mixture of 5 per cent mercury dimethyl vapour and 95 per cent nitrogen, in a Wilson chamber, has rather surprisingly yielded two definite cases of the production of pairs of positrons and electrons by β-particles of energy just greater than 1 MV. It is quite clear that phenomena of this kind would be very difficult to detect unless the bombarded element was in gaseous form. Measurement of the best pair gave the following result, where Eβ is the kinetic energy of the incident β-particle:

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  1. 1

    J. de Phys. et le Radium, 6, 1 (1935).

  2. 2

    Champion, Roy. Soc. Proc., A. 153, 353 (1936).

  3. 3

    Camb. Phil. Soc. Proc., 23, 935 (1927).

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