High-spin structure of ${}^{134}\text{Xe}$

Detailed spectroscopic information on the $N\sim 82$ nuclei is necessary to benchmark shell-model calculations in the region. The nuclear structure above long-lived isomers in ${}^{134}\mathrm{Xe}$ is investigated after multinucleon transfer (MNT) and actinide fission. Xenon-134 was populated as (i) a transfer product in ${}^{136}\text{Xe}+{}^{238}\text{U}$ and ${}^{136}\text{Xe}+{}^{208}\text{Pb}$ MNT reactions and (ii) as a fission product in the ${}^{136}\text{Xe}+{}^{238}\text{U}$ reaction employing the high-resolution Advanced Gamma Tracking Array (AGATA). Trajectory reconstruction has been applied for the complete identification of beamlike transfer products with the magnetic spectrometer PRISMA. The ${}^{136}\text{Xe}+{}^{198}\text{Pt}$ MNT reaction was studied with the $\gamma$-ray spectrometer GAMMASPHERE in combination with the gas detector array Compact Heavy Ion Counter (CHICO). Several high-spin states in ${}^{134}\mathrm{Xe}$ on top of the two long-lived isomers are discovered based on $\gamma \gamma$-coincidence relationships and information on the $\gamma$-ray angular distributions as well as excitation energies from the total kinetic energy loss and fission fragments. The revised level scheme of ${}^{134}\mathrm{Xe}$ is extended up to an excitation energy of 5.832 MeV with tentative spin-parity assignments up to ${16}^{+}$. Previous assignments of states above the $7^{-}$ isomer are revised. Latest shell-model calculations employing two different effective interactions reproduce the experimental findings and support the new spin and parity assignments.

Figure 1

Doppler-corrected $\gamma$-ray spectra gated on ${}^{134}\mathrm{Xe}$ identified in PRISMA (a) in the ${}^{136}\mathrm{Xe}+{}^{238}\mathrm{U}$ experiment and (b) in the ${}^{136}\mathrm{Xe}+{}^{208}\mathrm{Pb}$ experiment with indicated $\gamma$-ray energies in keV. The spectra are obtained with a cut on the prompt time peak between AGATA and PRISMA. Remaining contaminations of the U and Pb binary reaction partners are marked in the spectra. Italic numbers label newly observed $\gamma$-ray transitions.

Figure 2

Matrix of the time difference $\mathrm{\Delta }\mathrm{ToF}$ between PRISMA and DANTE plotted against the total kinetic energy loss for ${}^{134}\mathrm{Xe}$ events in the ${}^{136}\mathrm{Xe}+{}^{238}\mathrm{U}$ experiment. Transfer and fission are clearly separated. Note that for the fission channel, the computed TKEL is only qualitative since a binary reaction is assumed.

Figure 3

Doppler-corrected ${}^{134}\mathrm{Xe}$ $\gamma$-ray spectra from the ${}^{136}\mathrm{Xe}+{}^{238}\mathrm{U}$ experiment with (a) a gate on transferlike events and (b) events originating from actinide fission.

Figure 4

Ratio $W\left({\theta }_{\gamma ,\mathrm{Xe}}\right)$ from $\gamma$-ray angular distributions between the number of counts in the angular range from ${161}^{\circ }$ to ${180}^{\circ }$ over the number of counts in the ${150}^{\circ }$ to ${161}^{\circ }$ angular range, measured with AGATA in the ${}^{136}\mathrm{Xe}+{}^{238}\mathrm{U}$ experiment for various transitions in Xe isotopes (see labels). The horizontal line depicts the weighted mean ratio for evaluated $I\to I-2$ transitions. Dashed lines mark the corresponding standard deviation.

Figure 5

$\gamma \gamma$-coincidence spectrum of the ${}^{136}\mathrm{Xe}+{}^{238}\mathrm{U}$ experiment with a gate around $E_{\gamma }=1323$ keV (shown in the inset panel).

Figure 6

Doppler-corrected ${}^{134}\mathrm{Xe}$ $\gamma$-ray spectra with gates on low and large TKEL values from the ${}^{136}\mathrm{Xe}+{}^{208}\mathrm{Pb}$ experiment: (a) gate on low TKEL and (b) gate on large TKEL corresponding to higher excitation energies after the deep-inelastic MNT reaction. The applied gates on the TKEL distributions are shown in the insets. Both spectra are obtained with a cut on the prompt time peak between AGATA and PRISMA.

Figure 7

Partial experimental level scheme of ${}^{134}\mathrm{Xe}$ with the newly observed $\gamma$-ray transitions above the ${10}^{+}$ and $7^{-}$ isomers. Intensities of the yrast cascade below the isomer are extracted from the out-of-beam delayed $\gamma \gamma$ matrix and normalized to the $2_1^{+}$ decay; intensities above the isomer are extracted from the prompt matrix and normalized to the intensity of the 1323-keV transition. The intensity balance between the ground-state sequence and the high-spin states is extracted from the ${}^{136}\mathrm{Xe}+{}^{208}\mathrm{Pb}$ dataset.

Figure 8

(a) Sum of GAMMASHERE delayed-prompt $\gamma \gamma$-coincidence spectra with gates on the delayed 847-keV $2_1^{+}\to 0_1^{+}$, 884-keV $4_1^{+}\to 2_1^{+}$, and 861-keV $8_1^{+}\to 6_1^{+}$ yrast transitions (as indicated in the inset miniature levelscheme). (b) to (d): Prompt $\gamma \gamma$-coincidence spectra with gates on 218, 320, and 1323 keV. A closeup of the energy region around 320 keV is shown in the inset in panel (c).

Figure 9

Comparison of the experimental energy spectra (left panel) with the results of the shell-model calculations within the jj55 effective interaction (middle panel) and by Teruya et al. [51] (right panel). Note that in all panels the states are separated into three columns for the positive-parity, negative-parity, and higher-lying $2^{+}$ states.