Isomeric States of Po Isotopes in the Nanosecond Range Populated byPb(α, xn)Reactions

Abstract

Isomeric states of Po isotopes from $A=204\mathrm{}$ to $A=211\mathrm{}$ have been investigated by means of the nanosecond time analysis of $\mathrm{Pb}(\alpha , xn)$ $\gamma$ rays produced in natural beam bunches of a cyclotron. In addition to those already reported, new isomeric states have been revealed systematically. The following half-lives have been measured: ${}_{}{}^{204}{}_{}{}^{}\mathrm{Po}$: 190±20 nsec; ${}_{}{}^{206}{}_{}{}^{}\mathrm{Po}$: 160±40 nsec; ${}_{}{}^{208}{}_{}{}^{}\mathrm{Po}$: 380±100 nsec; and ${}_{}{}^{210}{}_{}{}^{}\mathrm{Po}$: 110±10 nsec. The possibility that such half-lives are associated with the expected 8+ state of predominant configuration ${h_{\frac{9}{2}}}^2\mathrm{}\left(p\right)\mathrm{}$ is discussed. Another half-life (24 nsec) found in ${}_{}{}^{210}{}_{}{}^{}\mathrm{Po}$ was assigned as a ($h_{\frac{9}{2}}{i}_{\frac{13}{2}}$) 11 - isomeric state. Odd isotopes show three-particle isomeric states in addition to the $i_{\frac{13}{2}}\mathrm{}\left(n\right)\mathrm{}$ isomeric state. Several characteristic features revealed in this study are discussed.