High-spin states in the five-valence-particle nucleus ${}^{213}\mathrm{Po}$

Excited states in ${}^{213}\mathrm{Po}$ have been populated using the ${}^{18}\mathrm{O}$$+$ ${}^{208}\mathrm{Pb}$ reaction at 85 MeV beam energy and studied with the Euroball IV $\gamma$ multidetector array. The level scheme has been built up to $~2.0$ MeV excitation energy and spin $I~25/2\hslash$ from the triple $\gamma$ coincidence data. Spin and parity values of several yrast states have been assigned from the $\gamma$ angular properties. The configurations of the yrast states are discussed using results of empirical shell-model calculations and by analogy with the neighboring nuclei. The spin and parity values of several low-spin states of ${}^{213}\mathrm{Po}$ previously identified from the $\beta$ decay of ${}^{213}\mathrm{Bi}$ are revised.

Figure 1

Spectra of $\gamma$ rays in double coincidence with (a) the first transition of ${}^{213}\mathrm{Po}$ (646 keV) and the $K$${\alpha }_1$ x ray of Po, (b) the 289 and 423 keV transitions, and (c) the 289 and 646 keV transitions.

Figure 2

Level scheme of ${}^{213}\mathrm{Po}$ determined in this work. The width of the arrows is representative of the relative intensity of the $\gamma$ rays. The level at 1504 keV is likely a long-lived state (see Sec. 4).

Figure 3

Top: Theoretical states belonging to the spherical $(\nu g_{9/2}){}^3$ configuration (a) and $(\pi h_{9/2}){}^2\otimes (\nu g_{9/2}){}^1$ configuration (b), computed using empirical interactions extracted from the two-nucleon neighboring nuclei (${}^{210}\mathrm{Pb}$,${}^{210}\mathrm{Po}$,${}^{210}\mathrm{Bi}$). The yrast states of the two sets are drawn in green and blue, respectively. Bottom: First excited states measured in the three-neutron nucleus ${}^{211}\mathrm{Pb}$ [1, 19] (c), and in the two-proton one-neutron nucleus ${}^{211}\mathrm{Po}$ [20, 21] (d). The yrast states of the two nuclei are drawn in green and blue, respectively. The wave functions of the 11/$2^{+}$ states (drawn in magenta) contain a large component of the $\nu i_{11/2}$ orbital located just above the $\nu g_{9/2}$ one.

Figure 4

Right: High-spin levels of ${}^{213}\mathrm{Po}$ identified in the present work. Left: Low-spin states measured in the $\beta$ decay of the 9/$2^{-}$ ground state of ${}^{213}\mathrm{Bi}$; the spin values (at variance with those assigned in Ref. [16]) are discussed in the text. The color code is the same as that of Fig. 3.