CXIII. Low intensity lines in the spectrum of the gamma-rays from 7 Li(p?) 8 Be(?) 4 He

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Abstract
Evidence for a γ-ray line at about 12·5 mev, in the 7Li(pγ) spectrum has been put forward recently by several workers. Although the measurements differ amongst themselves it appears that a line is present to about 10% of the intensity of the well known 17·6 mev component. Experiments in this laboratory have shown that, in addition to the broad 14·8 mev line, there are other transitions from the 17·6 mev state of 8Be to lower even states. The results were obtained by observing the emitted γ-ray coincidence with one of the α-particles resulting from the breakup of the even state. The measured α-particle ranges show that transitions occur to 8Be levels at 4·09, 5·31 ± 0 ·06 7·51 ± 0·06 mev. The corresponding γ-rays have energies of 13·54 mev, 12 ·32±0·06 and 10·12±0·06 mev and intensities of 2%, 2% and 0·5% of the total intensity. Backgrounds of soft x-radiation from the target backing, and energetic α-particles from the reaction 7Li(pα)4He complicated the experiment necessitating the performance of check experiments to ensure correct interpretation of the results. In particular the time of flight of the α-particles was used to give a rough indication of their energy and demonstrate the reliability of the coincidence counting.