BY analogy with the excitation and ionisation of atoms by light, one might expect that any complex nucleus should be excited or ‘ionised’, that is, disintegrated, by y-rays of suitable energy. Disintegration would be much easier to detect than excitation. The necessary condition to make disintegration possible is that the energy of the y-ray must be greater than the binding energy of the emitted particle. The y-rays of thorium C of v = 2-62 × 106 electron volts are the most energetic which are available in sufficient intensity, and therefore one might expect to produce disintegration with emission of a heavy particle, such as a neutron, proton, etc., only of those nuclei which have a small or negative mass defect; for example, D2, Be9, and the radioactive nuclei which emit a-particles. The emission of a positive or negative electron from a nucleus under the influence of y-rays would be difficult to detect unless the resulting nucleus were radioactive.
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Few-Body Systems (1991)