Long-LivedBi207and Energy Levels ofPb207

Abstract

The long-lived isotope of bismuth, ${\mathrm{Bi}}^{207}$, has been prepared by deuteron irradiation of lead and from the alpha-decay of ${\mathrm{At}}^{211}$. From the genetic relationship with ${\mathrm{At}}^{211}$, the half-life is estimated as 50 years. The conversion electron spectrum has been determined and is discussed in terms of the energy states of ${\mathrm{Pb}}^{207}$. Further evidence on these states has been obtained from the discovery of three rare alpha-groups in the decay of ${\mathrm{Po}}^{211}$ of energies 6.90, 6.57, and 6.34 Mev, which are compared with the main group at 7.43 Mev.