The Photodisintegration of the Deuteron by the Gamma-Radiation fromNa24

Abstract

The photodisintegration of the deuteron by the gamma-radiation from radioactive sodium ${\mathrm{Na}}^{24}$ has been observed in a cloud chamber filled with deuterium at a pressure of one atmosphere. A sample of NaF was activated by deuteron bombardment in the cyclotron to a gamma-ray strength equivalent to about 12 mg of radium, and was then brought close to the cloud chamber. Pictures were taken with a stereoscopic camera. Of the 100 proton tracks observed on 5000 pictures, only 42 were deemed suitable for range measurement, although the angular orientation of 61 could be determined. The range distribution of these tracks indicates a mean air equivalent range of 4.4 mm, corresponding to a mean energy of 410 kv for the photoprotons. This indicates that the difference between the energy of the ${\mathrm{Na}}^{24}$ gamma-ray and the binding energy of the deuteron is 820\ifmmode\pm\else\textpm\fi{}35 kv. Since the new range energy relation for slow protons has thrown doubt upon the binding energy of the deuteron, we can use the value of 3.00\ifmmode\pm\else\textpm\fi{}0.05 Mev obtained by the Compton recoil method for the energy of the gamma-radiation from ${\mathrm{Na}}^{24}$, and obtain 2.18\ifmmode\pm\else\textpm\fi{}0.07 Mev for the binding energy of the deuteron. The angular distribution of the tracks indicates that the disintegration is predominantly photoelectric, although a small contribution from the photomagnetic effect is not ruled out. A rough calculation from the yield of tracks indicates a cross section for the disintegration of 1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}27}$ ${\mathrm{cm}}^{2}$. The possibilities of the method for the determination of the energy of strong gamma-radiation is discussed.