Gamma Rays and Internal Pairs fromBe9+H1

Abstract

Gamma radiation following the reaction ${\mathrm{Be}}^9(p, \alpha ){\mathrm{Li}}^{6*}$, resonant at $E_p=2.56\mathrm{}$ Mev, has been studied with a magnetic lens spectrometer. The gamma-ray energy, determined from photo- and Compton-electron spectra, is found to be 3.572±0.012 Mev, not corrected for a possible 26-kev Doppler shift. The internal pair (positron) spectrum agrees most closely (to 4.5 percent) with the assignment of the radiation as magnetic dipole. Electric quadrupole is less likely and all other assignments are excluded. The magnetic-dipole character is consistent with the identification of the 3.57-Mev level of ${\mathrm{Li}}^6$ as the analog of the ${\mathrm{He}}^6$ ground state with $J=0^{+}$, $T=1\mathrm{}$. Reaction data are analyzed to suggest that the resonant state of the compound nucleus (the 8.89-Mev level of ${\mathrm{B}}^{10}$) has $J=2^{+}$, $T=1\mathrm{}$.