In-beam $\gamma$-ray spectroscopy of low- and medium-spin levels in ${}^{211}\mathrm{Po}$

The structure of the low- and medium-spin levels of the ${}^{211}\mathrm{Po}$ nucleus have been studied with in-beam $\gamma$-ray spectroscopy with the ${}^{208}\mathrm{Pb}(\alpha ,n){}^{211}\mathrm{Po}$ fusion-evaporation reaction. The level scheme was further extended with levels of the configurations $\pi {\left(h_{9/2}\right)}_{2^{+}-4^{+}}^2\otimes \nu g_{9/2}$, $\pi {\left(h_{9/2}\right)}_{8^{+}}^2\otimes \nu g_{9/2}$, $\pi {\left(h_{9/2}\right)}_{2^{+}-4^{+}}^2\otimes \nu i_{11/2}$, $\pi {\left(h_{9/2}\right)}_{2^{+}-4^{+}}^2\otimes \nu j_{15/2}$, $\pi {\left(h_{9/2}{f}_{7/2}\right)}_{8^{+}}\otimes \nu g_{9/2}$, and $\pi {\left(h_{9/2}\right)}_{0^{+}}^2\otimes \nu {\left(g_{9/2}\right)}_{0^{+}}^2{\left(s_{1/2}\right)}^{-1}$. The single-particle neutron states $\nu d_{5/2}$ and $\nu s_{1/2}$ were also identified. Furthermore, a number of states feeding the low-spin structures were added.

Figure 1

The total projection spectrum of the $E_{\gamma }\text{−}{E}_{\gamma }$ matrix. Only the most prominent peaks are marked with their energies. The presence of the ${}^{210}\mathrm{Po}$ nucleus is seen by the 245-keV peak and partly the 1181-keV peak while the ${}^{207}\mathrm{Pb}$ nucleus is noted by the 570-keV peak.

Figure 2

Partial level scheme showing the decay of levels above the 1427-keV and 1427+$\mathrm{\Delta }$ levels. New transitions are marked in red.

Figure 3

Partial level scheme portraying mainly the $\pi {\left(h_{9/2}\right)}_{2^{+}}^2\otimes \nu i_{11/2}$, $\pi {\left(h_{9/2}\right)}_{4^{+}}^2\otimes \nu i_{11/2}$, and $\pi {\left(h_{9/2}\right)}_{2^{+}}^2\otimes \nu j_{15/2}$ multiplets. New transitions are marked in red.

Figure 4

Partial level scheme depicting mainly the decay of levels above and connected the 1050-keV level. New transitions are marked in red.

Figure 5

Partial level scheme displaying transitions cascading through the 1181, 1122-, and 1160-keV levels. New transitions are marked in red.

Figure 6

Spectra obtained from the $E_{\gamma }\text{−}{E}_{\gamma }$ matrix of prompt transitions measured by JUROGAM I gated with selected transitions in ${}^{211}\mathrm{Po}$. Prominent transitions are marked with their energies in units of keV while chance coincidences and contaminants are marked with an asterisk. The transitions 363 and 570 keV in the 1064-keV gate and the 1064-keV transition in the 363-keV gate have been downsized by the amount indicated next to the peak in question.

Figure 7

Spectra were obtained from the $E_{\gamma }\text{−}{E}_{\gamma }$ matrix gated with selected transitions in ${}^{211}\mathrm{Po}$. Prominent transitions are marked with their energies in units of keV while chance coincidences and contaminants are marked with an asterisk. The scaled regions are marked by dashed lines and the amount of scaling done is shown by the corresponding number next to the arrows.

Figure 8

The $\pi {\left(h_{9/2}\right)}_{0^{+}-8^{+}}^2$ states and the $\pi {\left(h_{9/2}{f}_{7/2}\right)}_{8^{+}}$ state in ${}^{210}\mathrm{Po}$ are compared to the currently assigned states forming the equivalent $\pi {\left(h_{9/2}\right)}_{2^{+}-8^{+}}^2\otimes \nu g_{9/2}$ multiplets and the $\pi {\left(h_{9/2}{f}_{7/2}\right)}_{8^{+}}\otimes \nu g_{9/2}$ state in ${}^{211}\mathrm{Po}$. Note that the states next to the brackets are considered to have positive parity. The ${}^{210}\mathrm{Po}$ data is taken from Ref. [21].

Figure 9

Comparison of single-particle states and hole states in ${}^{207}\mathrm{Pb}$, ${}^{209}\mathrm{Pb}$, and ${}^{211}\mathrm{Po}$. The reference data for ${}^{207}\mathrm{Pb}$ are taken from Ref. [20], ${}^{209}\mathrm{Pb}$ data are taken from Refs. [24, 25, 26], and ${}^{211}\mathrm{Po}$ data are taken from Refs. [7, 9] and current work.