Isomer spectroscopy of ${}^{127}\mathrm{Cd}$

The spin and configurational structure of excited states of ${}^{127}\mathrm{Cd}$, the two-proton and three-neutron hole neighbor of ${}^{132}\mathrm{Sn}$, has been studied. An isomeric state with a half-life of 17.5(3) $\mu$s was populated in the fragmentation of a ${}^{136}\mathrm{Xe}$ beam on a ${}^9\mathrm{Be}$ target at a beam energy of 750 MeV/u. Time distributions of the delayed $\gamma$ transitions and $\gamma \gamma$ coincidence relations were exploited to construct a decay scheme. The observed yrast (19/2)${}^{+}$ isomer is proposed to have dominant configurations of $\nu (h_{11/2}^{-3})\pi (g_{9/2}^{-1},p_{1/2}^{-1})$, $\nu (h_{11/2}^{-2}{d}_{3/2}^{-1})\pi (g_{9/2}^{-2})$, and $\nu (h_{11/2}^{-2},s_{1/2}^{-1})\pi (g_{9/2}^{-2})$ and to decay by two competing stretched $M2$ and $E3$ transitions. Experimental results are compared with the isotone ${}^{129}\mathrm{Sn}$. The new information provides input for the proton-neutron interaction and the evolution of neutron hole energies in nuclei around the doubly magic ${}^{132}\mathrm{Sn}$ core.

Figure 1

Left: $Z$ information provided by the two ionization chambers. Right: $A/Q$ selection for Cd isotopes.

Figure 2

Singles $\gamma$-ray energy spectrum of ${}^{127}\mathrm{Cd}$. Background lines are marked with *. Inset: The sum of time distributions of the 711-, 739-, 821-, and 849-keV transitions with a single exponential decay fit.

Figure 3

$\gamma \gamma$ coincidence spectra with a coincidence window of 100 ns. Inset: Zoomed-in region of the respective weak coincidences.

Figure 4

Relative time distribution of the 739-keV transition with respect to the 821-keV transition. The spectrum shows a symmetric distribution.

Figure 5

The proposed level scheme for ${}^{127}\mathrm{Cd}$ and the theoretically calculated excited levels by SM and LSSM.