Band structure in ${}^{113}\mathrm{Sn}$

The structure of collective bands in ${}^{113}\mathrm{Sn}$, populated in the reaction ${}^{100}\mathrm{Mo}({}^{19}\mathrm{F},p5n)$ at a beam energy of 105 MeV, has been studied. A new positive-parity sequence of eight states extending up to 7764.9 keV and spin $(39/2^{+})$ has been observed. The band is explained as arising from the coupling of the odd valence neutron in the $g_{7/2}$ or the $d_{5/2}$ orbital to the deformed 2p-2h proton configuration of the neighboring even-$A$ Sn isotope. Lifetimes of six states up to an excitation energy of 9934.9 keV and spin $47/2^{-}\mathrm{belonging}$ to a $\mathrm{\Delta }I=2$ intruder band have been measured for the first time, including an upper limit for the last state, from Doppler-shift-attenuation data. A moderate average quadrupole deformation ${\beta }_2=0.22\pm 0.02$ is deduced from these results for the five states up to spin $43/2^{-}$. The transition quadrupole moments decrease with increase in rotational frequency, indicating a reduction of collectivity with spin, a feature common for terminating bands. The behavior of the kinematic and dynamic moments of inertia as a function of rotational frequency has been studied and total Routhian surface calculations have been performed in an attempt to obtain an insight into the nature of the states near termination.

Figure 1

Partial level scheme of ${}^{113}\mathrm{Sn}$ based on the present work. The level and $\gamma$-ray energies are given in keV. The relative intensities of the transitions are indicated by the widths of the arrows. New transitions are marked with asterisks.

Figure 2

Prompt $\gamma$-ray spectrum gated by the 322.0 keV $\gamma$ ray. The $\mathrm{\Delta }I=2$ transitions belonging to band 2 and the 796.8 keV $\gamma$ ray in band 4 (see text) are observed along with other $\gamma$ rays.

Figure 3

Prompt $\gamma$-ray spectra gated by the (a), (b) 416.7, (c) 1070.3, and (d) 1149.7 keV transitions, belonging to band 2; spectrum (e) shows the sum of the spectra gated by the 810.2, 811.6, and 930.2 keV transitions, belonging to band 3. Only the ${90}^{\circ }$ projection is shown in panel (e).

Figure 4

Gated DSA spectra for (a) 930.2, (b) 1026.9, and (c) 1037.1 keV transitions belonging to band 3. The upper (lower) panel shows spectra projected at ${148}^{\circ }$ (${90}^{\circ }$) with respect to the beam direction. Continuous lines are fits to the experimental data using the code lineshape [12]. Details are given in the text.

Figure 5

Plots of (a) the normalization factor $a$ in the polarization measurements and (b) the experimental polarization asymmetry $A$ (defined in the text) as a function of $\gamma$-ray energy.

Figure 6

Experimental Routhians $e^{\prime }$ for the $\alpha =-1/2$ (favored) and the $\alpha =+1/2$ (unfavored) signature partners of band 2.

Figure 7

Plot of transition quadrupole moments $Q_t$ for band 3 as a function of spin $I$.

Figure 8

Plots of dynamic moments of inertia $J^{\left(2\right)}$ for ${}^{109}\mathrm{Sn}$ [17] (open circles), ${}^{111}\mathrm{Sn}$ [1] (open squares), and ${}^{113}\mathrm{Sn}$ (from present work and Ref. [8]) (open triangles) for bands with the configuration [20,3] (see text). Plot of the kinematic moment of inertia $J^{\left(1\right)}$ for the [20,3] band in ${}^{113}\mathrm{Sn}$ is also shown using filled triangles.

Figure 9

Total-Routhian-surface plots for band 3 in the ${\beta }_2-\gamma$ plane for four rotational frequencies as indicated.