The ejection of protons from nitrogen on bombardment with α-particles of short range

U sing the expansion-cham ber m ethod, n inety p ro ton tracks are obtained from 850 pho to ­ graphs showing the d isintegration of nitrogen under bom bardm ent by slow a-particles. The num ber of disintegrations decreases as the energy of the a-particles is reduced, b u t the photographs show disintegrations occurring for energies less th an T7 MeV. The angular dis­ tr ibu tion is approxim ately isotropic for the protons ejected by a-particles of energy less th an 3 MeV, b u t there is a m arked preponderance a t about 90° for the protons ejected by a-particles of range abou t 2 cm. in air a t n .t .f . Typical photographs are reproduced.