Decay spectroscopy of ${}^{129}\mathrm{Cd}$

Excited states of ${}^{129}\mathrm{In}$ populated following the $\beta$ decay of ${}^{129}\mathrm{Cd}$ were experimentally studied with the GRIFFIN spectrometer at the ISAC facility of TRIUMF, Canada. A 480-MeV proton beam was impinged on a uranium carbide target and ${}^{129}\mathrm{Cd}$ was extracted using the Ion Guide Laser Ion Source (IG-LIS). $\beta$ and $\gamma$ rays following the decay of ${}^{129}\mathrm{Cd}$ were detected with the GRIFFIN spectrometer comprising the plastic scintillator SCEPTAR and 16 high-purity germanium (HPGe) clover-type detectors. From the $\beta \text{−}\gamma \text{−}\gamma$ coincidence analysis, 32 new transitions and seven new excited states were established, expanding the previously known level scheme of ${}^{129}\mathrm{In}$. The $logft$ values deduced from the $\beta$-feeding intensities suggest that some of the high-lying states were populated by the $\nu 0g_{7/2}\to \pi 0g_{9/2}$ allowed Gamow-Teller (GT) transition, which indicates that the allowed GT transition is more dominant in the ${}^{129}\mathrm{Cd}$ decay than previously reported. Observation of fragmented Gamow-Teller strengths is consistent with theoretical calculations.

Figure 1

The radioactive ion beam delivered to the spectrometer is implanted at the mutual centers of the detector arrays into the tape which is then moved and collected behind a lead wall (not shown in the figure).

Figure 2

The $\beta$-gated $\gamma$-ray spectrum with ${}^{129}\mathrm{Sn}$ transitions subtracted (see text for details). Single-escape peaks and double-escape peaks are labeled with “SE” and “DE”, respectively. The “#” symbol denotes the residue of the subtraction from a strong 2118.2-keV transition in ${}^{129}\mathrm{Sn}$.

Figure 3

The proposed level scheme of ${}^{129}\mathrm{In}$. Newly identified states and transitions are indicated by light gray (orange) color. Dark gray (blue) horizontal lines for the states at 451 and 1688 keV indicate isomeric states. Previously observed states or transitions are indicated by black color.

Figure 4

Observed $\gamma$-ray spectrum in coincidence with $\beta$ particles and the 994.9-keV transition.

Figure 5

Observed $\gamma$-ray spectrum in coincidence with $\beta$ particles and the 1835.6-keV transition, which provides evidence of the newly established level at 2134 keV. The “scattered $\gamma$-ray” peak arises from the strong 2118.3-keV transition [26] in ${}^{129}\mathrm{Sn}$, when part of the energy is absorbed in one HPGe crystal and the rest is detected by another HPGe crystal.

Figure 6

The half-life of the $17/2^{-}$ isomer measured by fitting the time difference of the timestamps of $\beta$ particles and $\gamma$ rays gated on 334.1-, 359.1-, 994.9-, and 1354.2-keV transitions. Both summed time distribution and the weighted average of these four time distribution yields a half-life of 10.8(1) $\mu \mathrm{s}$.

Figure 7

(Top) Time distribution of detected $\beta$ particles in a beam cycle, simultaneously fitted with the half-lives of ${}^{129}\mathrm{Cd}, {}^{129}\mathrm{In}$, and ${}^{129}\mathrm{Sn}$ (see text for details). In the figure, the half-life of ${}^{129}\mathrm{Cd}$ is set to be 153.6 ms and this half-life results in the best fit. (Bottom) Fit residual distribution.

Figure 8

Distributions of $logft$ values for allowed transitions and first-forbidden (ff) transitions in odd-$A {}^{121\text{−}131}\mathrm{In}$ and ${}^{121\text{−}125}\mathrm{Cd}$, based on the data from ENSDF [26].

Figure 9

Observed Gamow-Teller (GT) strength $B\left(\mathrm{GT}\right)$ in comparison with the calculated distribution for the $11/2^{-}$ (top) and $3/2^{+}$ (bottom) states in ${}^{129}\mathrm{Cd}$. The red circles show the results obtained in Ref. [14]. The calculation is identical to the work shown in there.