Portal de Periódicos da CAPES

Emission of Neutrons from Argon, Chlorine, Aluminum and Some Heavier Elements Under Alpha-Particle Bombardment

1938; American Institute of Physics; Volume: 53; Issue: 5 Linguagem: Inglês

10.1103/physrev.53.351

1536-6065

Ernest C. Pollard, H. L. Schultz, Gordon Brubaker,

Nuclear physics research studies

The emission of neutrons from chlorine, argon, scandium, titanium, manganese and iron under alpha-particle bombardment was established. The yield from argon is considerable and enabled a measurement of the energy of the neutrons to be made: the majority are associated with a group of energy change -5.6\ifmmode\pm\else\textpm\fi{}1.0 Mev, but two groups must be present. The excitation curve for these neutrons was plotted for alpha-particle energies between 3.5 and 9.0 Mev and varies smoothly in agreement with penetration through a barrier of radius 7.6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm. This smooth variation means that the total neutron yield does not change rapidly as a new group is excited, from which it is deduced that observations on single groups would show apparent resonance effects. The excitation curve for chlorine fits a theoretically derived function for a nuclear radius of 6.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm and a similarly plotted curve for aluminum agrees with a radius of 5.8\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm. These last elements have radii approximately fitting the formula $R={R}_{0}{A}^{\frac{1}{3}}$ with ${R}_{0}=1.94\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$, while argon has a radius which is definitely too large to fit the above relation. This abnormally large radius is linked with the large neutron content of the argon nucleus.