Masses of ground and isomeric states of ${}^{101}\mathrm{In}$ and configuration-dependent shell evolution in odd-$A$ indium isotopes

We report first precision mass measurements of the $1/2^{-}$ isomeric and $9/2^{+}$ ground states of ${}^{101}\mathrm{In}$. The determined isomeric excitation energy continues a smooth trend of odd-$A$ indium isotopes up to the immediate vicinity of $N=50$ magic number. This trend can be confirmed by dedicated shell-model calculations only if the neutron configuration mixing is considered. We find that the single-particle energies are different for different states of the same isotope. The presented configuration-dependent shell evolution, type-II shell evolution, in odd-$A$ nuclei is discussed for the first time. Our results will facilitate future studies of single-particle neutron states.

Figure 1

Part of the revolution time spectrum zoomed in a time window of $668\mathrm{ns}\le t\le 672\mathrm{ns}$. The nuclides with well-known masses (black color) were used as calibrants in the mass calibration. The inset shows the well-resolved peaks of the ground and isomeric states of ${}^{101}\mathrm{In}$.

Figure 2

Excitation energies of the $1/2^{-}$ isomers in odd-$A$ indium isotopes together with shell-model calculations. The filled squares are experiment data from ENSDF [38] and the filled circle for the present Rapid Communication. The green line is obtained by adding valence neutrons only to the $\nu 2d_{5/2}$ orbital, whereas the blue line corresponds to the $\nu 1g_{7/2}$ occupation only. The red line is calculated within the model space of $\nu 1g_{7/2},\nu 2d_{5/2},\nu 2d_{3/2},\nu 3s_{1/2}$, and $\nu 1h_{11/2}$ orbitals.

Figure 3

Neutron occupation numbers for the $9/2^{+}$ ground states in odd-$A$ indium isotopes from ${}^{101}\mathrm{In}$ to ${}^{113}\mathrm{In}$.

Figure 4

Neutron occupation numbers for the $1/2^{-}$ states in odd-$A$ indium isotopes from ${}^{101}\mathrm{In}$ to ${}^{113}\mathrm{In}$.

Figure 5

Neutron effective single-particle energies of $\nu 1g_{7/2}$ with respect to $\nu 2d_{5/2}$ for $9/2^{+}$ and $1/2^{-}$ states in indium isotopes as calculated with the $V_{\mathrm{MU}}+\mathrm{LS}$ interaction.