The Energy of Gamma-Rays Accompanying the Decay ofBe7

Abstract

Coincidence counter measurements have been made on the absorption of secondary electrons produced by the gamma-rays accompanying the decay of ${\mathrm{Be}}^7$. The gamma-rays from the annihilation of ${\mathrm{N}}^{13}$ positrons were used for calibration of the absorbing system. The maximum ranges in aluminum are respectively 0.86±0.04 mm for the annihilation radiation and 0.77±0.03 mm for that due to ${\mathrm{Be}}^7$. The energy of the latter was found to be 0.485±0.005 Mev by assuming gamma-rays of 0.510 Mev from ${\mathrm{N}}^{13}$. The agreement between the experimental result and the low excited level of ${\mathrm{Li}}^7$ (0.475 Mev) deduced from other reactions confirms the suggestions of previous authors that the observed gamma-rays from ${\mathrm{Be}}^7$ originate from this excited state of ${\mathrm{Li}}^7$ which is created by electron capture.