Excited States of the Mirror Nuclei Be⁷ and Li⁷

Citation

Brown, Alfred Bruce (1950) Excited States of the Mirror Nuclei Be⁷ and Li⁷. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/5SND-CQ07. https://resolver.caltech.edu/CaltechETD:etd-08252008-142317

Abstract

A low energy group of alpha particles has been found to result from the reaction B¹⁰(p α)Be^7*, indicating the existence of an excited state of Be⁷. Observation of this group and separation of the group from protons elastically scattered by the thin B¹⁰ targets was made possible through high resolution magnetic analysis supplemented by absorption techniques. The excitation of the state is 0.434 ± .005 Mev, and the Q-value of the reaction to the ground state is 1.148 ± .006 Mev. The Q-value of the reaction to the excited state is thus 0.714 ±.008 Mev. On the basis of approximately equal neutron-neutron and proton-proton forces, the energy difference between the ground states of Li⁷ and Be⁷ can be accounted for as electro-static eneray, using a reasonable value of average separation of protons in the two nuclei. The energy difference between the state in Be⁷ at 0.434 Mev and the state in Li⁷ at 0.478 Mev can be similarly accounted for, if a small increase in the size of the nuclei over their size in the ground state is assumed. These results indicate that the ground states of the two nuclei may be considered corresponding states, and that the excited states may also be so considered. In the reaction to the excited state in Be⁷ a resonance of about 0.28 Mev width exists at 1.51 Mev proton energy, and is observed in the yield of both alpha particles and gamma rays. In the reaction to the ground state there is a resonance 0.55 Mev wide at 1.06 Mev proton energy, and there is some indication of another at about 1.5 Mev.

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