Decay ofBi207

The gamma rays of 8.0-year ${\mathrm{Bi}}^{207}$ have been studied with single-crystal and coincidence scintillation spectrometers. The measured relative intensities of the 0.570-, 1.07-, and 1.77-Mev transitions are 1, 0.84±0.06, and 0.096±0.007, respectively. Upper limits on the intensity of a 2.40-Mev and of a 1.47-Mev gamma ray of 0.05 percent and 0.2 percent (see note added in proof on page 713), respectively, of the 1.77-Mev gamma ray have been obtained. Coincidence spectrometry with the lead $K$ x-rays indicates pure $L$-electron capture to the 2.34-Mev state and 2.8±0.3 percent $K$-electron capture to the 0.570-Mev level. Other coincidence measurements agree quantitatively with the proposed decay scheme. The angular correlation of the 1.77-0.570-Mev cascade has been measured and is also in agreement with the proposed decay scheme.