arXiv subjects

T. Stetz

Publications and source records attributed to T. Stetz.

5 recordsLinked to original sources

arXiv2026

Sizeable mixing between the coexisting normal and intruder structures of $^{96}$Zr revealed through lifetime measurements

Lifetimes of excited states of the nucleus $^{96}$Zr were studied with the Doppler-shift attenuation method following the $^{94}$Zr($^{18}$O,$^{16}$O)$^{96}$Zr two-neutron transfer reaction. The obtained $B(E2;2^+_2\to0^+_2)$ and $B(E2;4^+_1\to2^+_2)$ transition strengths, amounting to $26(2)$ and $39(7)$\,W.u., respectively, firmly attribute the $2^+_2$ and $4^+_1$ states to the collective intruder band built on top of the $0^+_2$ state. The nature of this structure is discussed against predictions of the collective model using the Bohr Hamiltonian, the interacting boson model with configuration mixing, and the quasiparticle vacua shell model. The collective, interband $B(E2;4^+_1\to2^+_1)=11.2(8)$\,W.u. transition strength, refuting the previously assumed purity of both structures, is reproduced in the calculations. The quasiparticle vacua shell model predicts, in agreement with a simple two-state model based on experimental $E2$ transition strengths, considerable mixing between the normal and intruder $2^+$ states.

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arXiv2026

Lifetime of the $4^+_1$ state of $^{132}$Te

The evolution of the collectivity of tellurium isotopes from mid-shell towards $N=82$ is currently based mainly on properties of the first excited $2^+$ states. To extend structural information in this isotopic chain, in particular with respect to the balance of microscopic, seniority-type and collective excitations, electric quadrupole transition strengths from $4^+$ states need to be considered. An experiment was performed to determine the $4_1^+$ lifetime of $^{132}$Te via the recoil-distance Doppler-shift method at the University of Cologne tandem accelerator. The isotope of interest was populated in the two neutron-transfer reaction $^{130}$Te($^{18}$O,$^{16}$O)$^{132}$Te$^*$. The $E2$ decay transition strength has been determined to be $B(E2; 4^+_1\rightarrow 2^+_1) = 9.3(10)\, \text{W.u.}$ and compares favourably to shell model calculations.

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arXiv2025

Lifetimes of the $2^+_1$ and $4^+_1$ states of the neutron-rich nuclide $^{200}$Pt

The lifetimes of the $2^+_1$ and $4^+_1$ states of $^{200}$Pt were measured applying the recoil-distance Doppler-shift method. Excited states were populated in the $^{198}$Pt($^{18}$O, $^{16}$O)$^{200}$Pt two-neutron transfer reaction at the $9\,\text{MV}$ tandem accelerator at the IFIN-HH in Măgurele, Romania. The resulting $B(E2)$ values of the $2^+_1 \rightarrow 0^+_1$ and $4^+_1 \rightarrow 2^+_1$ transitions as well as the $B_{4/2}$ ratio of $2.08(32)$ indicate the nuclear structure evolving towards sphericity when approaching the neutron shell closure at $N = 126$. The $B(E2; 2^+_1 \rightarrow 0^+_1)$ values of Pt and Hg are compared to values of Te, Xe and Ba as both regions of the nuclear chart show similar structural effects.

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arXiv2025

Isolated one-phonon mixed-symmetry 2+ state of the radioactive neutron-rich nuclide 132Te

The $M1$ transition strengths between excited $2^+$ states of the neutron-rich, radioactive nuclide $^{132}$Te have been studied through direct lifetime measurements using the Doppler-shift attenuation method in a two-neutron transfer reaction on a $^{130}$Te target. An unambiguous identification of the lowest-lying mixed-symmetry $2^+$ state has been achieved on the basis of the large $B(M1;2^+_2\rightarrow2^+_1$)=0.18(2) $μ_\mathrm{N}^2$ transition strength, in agreement with shell-model calculations. Results are compared to the shell model, and the analysis of both, data and calculations, unambiguously identifies the second-excited $2^+$ state of $^{132}$Te as the one-quadrupole phonon mixed-symmetry state of this isotope. A lowering of the energy and $B(M1;2^+_\mathrm{ms}\rightarrow 2^+_1)$ strength within the $N$=80 isotones toward the $Z$=50 shell closure is observed, which goes alongside with the lowering of the $E2$ collectivity approaching the magic proton shell.

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arXiv2025

Revised $B(E2; 2^{+}_{1} \rightarrow 0^{+}_{1})$ value in the semi-magic nucleus $^{210}$Pb

The lifetime of the $2^+_1$ state of $^{210}$Pb was measured in the $^{208}$Pb($^{18}$O, $^{16}$O)$^{210}$Pb two-neutron transfer reaction by $γ$-ray spectroscopy employing the recoil-distance Doppler-shift method. The extracted absolute $B(E2)$$\downarrow$ value of ${119\;^{+\;9}_{-\;8}\;\hspace{-0pt}\,\text{e}^2\text{fm}^4}$ is consistent with previously reported measurements, but with significantly improved precision. The available experimental data for the $2^+_1$-$4^+_1$-$6^+_1$-$8^+_1$ multiplet are compared with shell-model calculations based on the well-established Kuo-Herling interaction. The new $B(E2)$$\downarrow$ value agrees well with the shell-model prediction, providing evidence that the properties of the $2^+_1$ and $8^+_1$ states of $^{210}$Pb can be consistently described together within the nuclear shell-model framework.

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