Chronology of Milestone Events in Particle Physics - CHADWICK 1934
Chronology of Milestone Events in Particle Physics

CHADWICK 1934

Chadwick, J.; Goldhaber, M.;
A Nuclear Photoeffect: Disintegration of the Diplon by Rays
Nature 134 (1934) 237;

Motivation
By analogy with the excitation and ionization of atoms by light, one might expect that any complex nucleus should be excited or "ionized'', that is, disintegrated, by -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 -ray must be greater than the binding energy of the emitted particle. The -rays of thorium C' ' of h = 2.62 x 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 -particles. The emission of a positive or negative electron from a nucleus under the influence of -rays would be difficult to detect unless the resulting nucleus were radioactive.
Heavy hydrogen was chosen as the element first to be examined, because the diplon has a small mass defect and also because it is the simplest of all nuclear systems and its properties are as important in nuclear theory as the hydrogen atom is in atomic theory. (Extracted from the introductory part of the paper.).

Accelerator SOURCE Detectors CLOUD, CNTR

Reactions
  deuteron p n 1.8,2.62 MeV (Plab) cs

Particles studied
  n mass

Record comments
Evidence for deuteron photodisintegration. First precise measurements of the neutron mass.
    
  New Comments List of Comments

javier.castelo@uab.es First photonuclear reaction observed !