Three new isotopes of polonium have been prepared by bomarding isotope-enriched lead samples with helium ions and bismuth with protons and deuterons. Evidence is given for their assignments as follows: The 9-day ${\mathrm{Po}}^{206}$ has been shown to decay to 6.4-day ${\mathrm{Bi}}^{206}$. No daughter activities of ${\mathrm{Po}}^{207}$ and ${\mathrm{Po}}^{208}$ have been found. No activity has been found for ${\mathrm{Po}}^{209}$. Also, 110-min. ${\mathrm{F}}^{18}\left({\beta }^{+}\right)$ has been prepared by the reaction ${\mathrm{O}}^{16}(\alpha ,pn){\mathrm{F}}^{18}$ or ${\mathrm{O}}^{16}(\alpha ,2n){\mathrm{Ne}}^{18}\stackrel{\mathrm{short}}{\to }{\mathrm{F}}^{18}$.

• Received 18 July 1947

DOI:https://doi.org/10.1103/PhysRev.72.758