Liberation of Neutrons in the Nuclear Explosion of Uranium

Abstract

RECENT experiments^1,2 have revealed the existence of a new kind of nuclear reaction: neutron bombardment of uranium and thorium loads to an explosion of the nucleus, which splits up into particles of inferior charge and weight, a considerable amount of energy being liberated in this process. Assuming a partition into two particles only, so that the nuclear mass and charge of uranium have to be distributed between two lighter nuclei, the latter contain considerably more neutrons than the heaviest stable isotopes with the same nuclear charges. (A splitting into, for example, ⁹⁸Rb and ¹⁴¹Cs means an excess of 11 neutrons in the first, and of 8 neutrons in the second of these two nuclei.) There seem to be two possibilities, of getting rid of this neutron excess. By the emission of a α′-ray, a neutron is transformed into a proton, thus reducing the neutron excess by two units; in the example given above, five and four successive α′-activities respectively would be needed to restore the neutron-proton stability ratio. In fact, the explosion products have been observed to be α-active and several periods have been recorded, so that a part, at least, of the neutron excess is certainly disposed of in this way. Another possible process is the direct liberation of neutrons, taking place either as a part of the explosion itself, or as an “evaporation” from the resulting nuclei which would be formed in an excited state.