SEARCH FOR A 3.20 MEV. γ-RAY IN THE DISINTEGRATION OF THORIUM C″

Abstract

In about 70% of the disintegrations, thorium C″ transforms to the ground state of thorium D by the emission of a β-ray and two successive γ-rays of energy 0.58 and 2.62 Mev. A search has been made for a γ-ray of energy 3.20 Mev. which would be emitted if a single radiative transition occurred. Using a source of radiothorium in equilibrium with its decay products, the secondary electrons ejected by the γ-rays from thin radiators of lead and uranium were analyzed in a magnetic lens spectrometer. No photoelectrons ejected by a 3.20 Mev. γ-ray were observed. If the γ-ray occurs its intensity is less than 0.2% of the intensity of the γ-ray at 2.62 Mev. This result is discussed in the light of the proposed disintegration schemes of thorium C″.