arXiv subjects

K. E. Ide

Publications and source records attributed to K. E. Ide.

7 recordsLinked to original sources

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

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

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

Deviations from the Porter-Thomas Distribution due to Nonstatistical $γ$ Decay below the $^{150}$Nd Neutron Separation Threshold

We introduce a new method for the study of fluctuations of partial transition widths based on nuclear resonance fluorescence experiments with quasimonochromatic linearly polarized photon beams below particle separation thresholds. It is based on the average branching of decays of $J=1$ states of an even-even nucleus to the $2^+_1$ state in comparison to the ground state. Between 5 and 7 MeV, a constant average branching ratio for $γ$ decays from $1^-$ states of 0.490(16) is observed for the nuclide $^{150}$Nd. Assuming $χ^2$-distributed partial transition widths, this average branching ratio is related to a degree of freedom of $ν= 1.93(12)$, rejecting the validity of the Porter-Thomas distribution, requiring $ν=1$. The observed deviation can be explained by nonstatistical effects in the $γ$-decay behavior with contributions in the range of 9.4(10)% up to 94(10)%.

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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 $\gamma$-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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arXiv2025

Gamma decay of the $^{154}$Sm Isovector Giant Dipole Resonance: Smekal-Raman Scattering as a Novel Probe of Nuclear Ground-State Deformation

Gamma decays of the isovector giant dipole resonance (GDR) of the deformed nucleus $^{154}$Sm from $2^+_1$-Smekal-Raman and elastic scattering were measured using linearly polarized, quasimonochromatic photon beams. The two scattering processes were disentangled through their distinct angular distributions. Their branching ratio and cross sections were determined at six excitation energies covering the $^{154}$Sm GDR. Both agree with the predictions of the geometrical model for the GDR and establish $γ$ decay as an observable sensitive to the structure of the resonance. Consequently, the data place strong constraints on the nuclear shape, including the degree of triaxiality. The derived $^{154}$Sm shape parameters $β=0.2926(26)$ and $γ=5.0(14)$ agree well with other measurements and recent Monte Carlo Shell-Model calculations.

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arXiv2023

Measurement of the Isolated Nuclear Two-Photon Decay in $^{72}\mathrm{Ge}$

The nuclear two-photon or double-gamma ($2γ$) decay is a second-order electromagnetic process whereby a nucleus in an excited state emits two gamma rays simultaneously. To be able to directly measure the $2γ$ decay rate in the low-energy regime below the electron-positron pair-creation threshold, we combined the isochronous mode of a storage ring with Schottky resonant cavities. The newly developed technique can be applied to isomers with excitation energies down to $\sim100$\,keV and half-lives as short as $\sim10$\,ms. The half-life for the $2γ$ decay of the first-excited $0^+$ state in bare $^{72}\mathrm{Ge}$ ions was determined to be $23.9\left(6\right)$\,ms, which strongly deviates from expectations.

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