The transformation of the nitrogen isotope of mass 15 into carbon and helium by bombardment with protons

Abstract

Measurements of the ‘cross-section’ of the nuclear reaction N 15 (p, α) C 12 have been made for protons with different values of the energy in the interval between 200 and 450 keV. There are indications of a broad maximum, in the curve showing the variation of ‘cross-section’ with energy, in the neighbourhood of 400 keV, with a width of 150 keV. The partial proton width of the maximum is 250 eV. Extrapolation of the one-level dispersion formula, together with the theory of thermonuclear reactions, gives a lifetime of 3 x 10 4 years for N 15 in the sun. A photographic method of determining the angular distribution of the emitted α-particles is described. The angular distribution near 400 keV is found to be approximately isotropic, the deviations from isotropy being, at most, 10%.