Gamma-Rays fromBe9(α,n)

The gamma-ray spectrum produced by bombarding ${\mathrm{Be}}^9$ with polonium alpha-particles has been analyzed by means of a 180° focusing pair spectrometer. The spectrum shows a single gamma-ray of energy 4.45±0.09 Mev. The 6.7-Mev gamma-ray reported by earlier observers is not detected: no gamma-rays are present in the range 6 to 11 Mev to the extent of one-half percent of the 4.45-Mev intensity. Although no gamma-rays were detected below 4.45 Mev, the sensitivity of the spectrometer is much smaller in this low energy region, and the 2.7-Mev gamma-ray reported by Bothe and Dzelepov would probably not be detected if present. The $\mathrm{Th}{C}^{\prime \prime }$ gamma-radiation, investigated as a check on the operation of the spectrometer, is measured as 2.62±0.06 Mev; no gamma-radiation is detectable in the vicinity of 3.2 Mev with intensity as great as one-half percent of that of the 2.62-Mev gamma-ray.