High-spin intruder band in ${}^{107}\mathrm{In}$

High-spin states in the neutron-deficient nucleus ${}^{107}\mathrm{In}$ were studied via the ${}^{58}\mathrm{Ni}$(${}^{52}\mathrm{Cr}$,3p) reaction. In-beam $\gamma$ rays were measured using the JUROGAM detector array. A rotational cascade consisting of ten $\gamma$-ray transitions, which decays to the 19/$2^{+}$ level at 2.002 MeV, was observed. The band exhibits the features typical for smooth terminating bands that also appear in rotational bands of heavier nuclei in the $A\hspace{0.5em}~$ 100 region. The results are compared with total Routhian surface and cranked Nilsson-Strutinsky calculations.

Figure 1

Total $\gamma$-$\gamma$ coincidence spectrum. Gamma-ray peak energies are labeled in keV for strong peaks. Previously known transitions in ${}^{107}\mathrm{In}$ as well as those from the other principal evaporation residues, ${}^{104}\mathrm{Cd}$, ${}^{106}\mathrm{In}$, and ${}^{107}\mathrm{Sn}$, are observed as indicated in the figure.

Figure 2

A level scheme of ${}^{107}\mathrm{In}$ constructed in the present study. Transitions below dashed lines were previously identified [8]. Insets (a)–(d) represent the typical angular distribution of $\gamma$ transitions observed with the present setup. Solid lines are the fitted curve of the angular distribution function $W(\theta )$.

Figure 3

Gamma-ray energy spectrum gated by the 1428- and 159-keV transitions. The inset enlarges the region between 600 keV and 1 MeV.

Figure 4

Gamma-ray energy spectrum gated by the 1532- and 316-keV transitions. The inset enlarges the region between 350 and 650 keV.

Figure 5

Sum of $\gamma$-ray energy spectra created by double gating on the in-band transitions of the rotational band (STB1). The inset enlarges the region between 1.45 and 2.5 MeV.

Figure 6

Gamma-ray energy spectrum gated by the 2331-keV linking transition from the $\gamma$-$\gamma$ matrix.

Figure 7

Gamma-ray energy spectrum created by gating on the in-band transition of the rotational band in one axis, and the 946-, 791-, 150-, 438-, 413-, 1000-, and 1414-keV transitions in the other axis of the $\gamma \gamma \gamma$ cube. The insets enlarge the regions from 0.5 to 0.7 MeV, and from 1.45 to 1.65 MeV, respectively.

Figure 8

Excitation energies of the yrast levels and the levels in the rotational band as a function of spin (upper panel). Relative intensities of yrast $\gamma$ transitions and those of the band are plotted as a function of spin in the lower panel.

Figure 9

A plot of $a_2$ and $a_4$ coefficients of $\gamma$-ray angular distributions, $W(\theta )=a_0$[$1+a_2$$P_2$(cos$\theta$) $+a_4$$P_4$(cos$\theta$)], as a function of $\gamma$-ray energy. Here, $\theta$ is the emission angle of $\gamma$ rays relative to the beam axis and $P_n$(cos$\theta$) are the Legendre polynomials. Solid circles and solid triangles correspond to the angular distribution of known M1 and $\Delta I=0$ E1 transitions, respectively. Open circles indicate those of the transitions below the isomeric state at 1.852 MeV. Open triangles correspond to those of the identified in-band transitions as well as the known E2 transition (1144 keV). The open square is for the case of the 2331-keV linking transition.

Figure 10

${\chi }^2$ versus tan${}^{-1}\delta$ curves for the 2331-keV transition in ${}^{107}\mathrm{In}$. The parameters indicated were used to compute the curves.

Figure 11

Experimentally deduced dynamical moments of inertia $J$${}^{(2)}$ in ${}^{107}\mathrm{In}$, ${}^{108}\mathrm{Sn}$, and ${}^{109}\mathrm{Sb}$. The data on ${}^{107}\mathrm{In}$ are from the present work.

Figure 12

Calculated total Routhian surfaces (TRS) at a rotational frequency of 0.75 MeV. The lowest positive-parity configurations with signature $+$1/2 and $-$1/2 are shown in the left and right upper panels, respectively, whereas the lowest negative-parity configuration with signature $-$1/2 is plotted on the lower left panel.

Figure 13

Comparison of experimental and calculated excitation energies, $J$${}^{(1)}$ and $J$${}^{(2)}$ moments of inertia as a function of rotational frequency. The highest-frequency data point, which is originated from the tentatively assigned 1970-keV transition, is also included in the plot. Theoretical values were obtained by TRS calculations. The dashed line marks the rigid-body moment of inertia for a deformation parameter ${\beta }_2\hspace{0.5em}=\hspace{0.5em}$0.25.

Figure 14

Calculated energies of the configurations forming the yrast line in four combinations of parity and signature shown relative to rigid rotor reference. Large open circles indicate terminating and aligned states. Solid and dashed lines are used for positive and negative parity states, respectively. Solid and open symbols are used for the signatures $\alpha \hspace{0.5em}=\hspace{0.5em}+1/2$ and $\alpha \hspace{0.5em}=\hspace{0.5em}-1/2$, respectively. Configuration labels are shown in the legend.

Figure 15

Comparison between the experimentally observed $\Delta I=2$ rotational band (STB1) and the CNS predictions for selected configurations. The top panel shows the experimental band with different spin assignments $I_0$ for the lowest observed state. The middle panel shows the chosen predicted configurations. The bottom panel plots the energy difference between the predictions and observations.

Figure 16

Evolution of the potential energy surfaces (PES) for the [$20,2$] configuration in ${}^{107}\mathrm{In}$. The six PES figures are given in steps of $4\hslash$ from the near-prolate state at $I=13.5^{+}$ up to the terminating state at $I=33.5^{+}$. The energy difference between two neighboring equipotential lines is 0.2 MeV and the last equipotential line corresponds to 4.0-MeV excitation with respect to the minimum.