arXiv subjects

K. Hadyńska-Klęk

Publications and source records attributed to K. Hadyńska-Klęk.

5 recordsLinked to original sources

arXiv2025

First evidence for the J$>$1 components of the pygmy dipole resonance in neutron-rich nuclei

Gamma ($γ$) decay shapes the synthesis of heavy elements in neutron-rich nuclear environments of neutron star mergers, supplying the Universe with heavy elements. The low-energy pygmy dipole resonance (PDR) influences nuclear reaction rates of the rapid nucleosynthesis through enhanced $γ$ transitions. However, since it is difficult to reproduce astrophysical conditions in laboratories, PDR was previously observed only in $J = 1$ spin states. Here we report the first experimental observation of $J > 1$ components of PDR, identified in the $β$-delayed $γ$ decay of the J$^π$ = 3$^{-}$ spin-parity isomer of $^{80}$Ga. The data analysis, combined with decay information and theoretical calculations allows the identification of resonant structures below the neutron emission threshold of the neutron-rich germanium $^{80}$Ge as J$^π = (2,3)^-$ components of the PDR built on the low-lying J$^π$ = 2$^+$ quadrupole state. Our findings extend the concept of PDR beyond dipole states, with implications for nuclear structure theory and experiment, as well as the element production in the cosmos.

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arXiv2025

$β$-delayed spectroscopy of $^{80}$Ge$_{48}$ and competition between Gamow-Teller and first-forbidden transitions in $^{80g+m}$Ga$_{49}$ $β$ decay

The $β$-delayed spectroscopy of $^{80}$Ge has been studied using sources of ground and low-lying isomeric states of $^{80}$Ga. A hybrid $γ$-ray spectrometer was used, composed of high-purity germanium (HPGe) detectors for low-energy $γ$-ray detection, phoswich detectors from the PARIS array for high-energy $γ$ rays and a plastic detector for $β$ tagging. The new decay level schemes are presented, with 13 and 14 states $β$ populated by $^{80g}$Ga and $^{80m}$Ga, respectively, being reported for the first time. We quantitatively compare summed intensities of first-forbidden and previously reported Gamow-Teller $β$ transitions [R. Li et al., \href{https://doi.org/10.1103/PhysRevC.111.034303}{Phys. Rev. C 111, 034303 (2025)}]. The upper-limit fractions of first-forbidden transitions contributing to the decays of $^{80g}$Ga and $^{80m}$Ga are (48.0 $\pm$ 2.7)$\%$ and (47.9 $\pm$ 3.3)$\%$ of the observed total $β$ transition intensities of (78.2 $\pm$ 2.5)$\%$ and (82.2 $\pm$ 3.7)$\%$, respectively. Notably, the half-lives decrease in accordance with the upper limits of (48.0 $\pm$ 6.0)$\%$ [3.67(20) s $\rightarrow$ 1.91(3) s] and (47.9 $\pm$ 7.2)$\%$ [3.01(19) s $\rightarrow$ 1.57(1) s] for $^{80g}$Ga and $^{80m}$Ga, respectively, when including first-forbidden transitions, in contrast to those by Gamow-Teller transitions only.

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arXiv2025

Simultaneous impacts of nuclear shell structure and collectivity on $β$ decay: Evidence from $^{80}$Ga$_{49}$

The Gamow-Teller strength distribution covering the entire $β$-decay window, up to 10.312(4) MeV, of $^{80g+m}$Ga was measured for the first time in photo fission of UC$_x$ induced by a 50 MeV electron beam. The new data show significant enhancement in the high-energy region with a jump structure. Simultaneously, the $γ$ deexciting behavior of $β$-populated states presents a competition between deexcitation to 2$_1^+$ [$β_2$ = 0.155(9)] and to 2$_2^+$ [$β_2$ = 0.053$_{0.009}^{0.008}$)] in $^{80}$Ge. To understand these data, we performed a realistic shell-model calculation and systematic analysis of log $\it{ft}$ ratios between precursors' $β$ decay to 2$_2^+$ and to 2$_1^+$ of Ga isotopes. We conclude that these phenomena evidence simultaneous impacts of nuclear shell structure and collectivity on $\it{B}$(GT) distribution and therefore the half-life of the precursor.

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arXiv2019

$^{78}$Ni revealed as a doubly magic stronghold against nuclear deformation

Nuclear magic numbers, which emerge from the strong nuclear force based on quantum chromodynamics, correspond to fully occupied energy shells of protons, or neutrons inside atomic nuclei. Doubly magic nuclei, with magic numbers for both protons and neutrons, are spherical and extremely rare across the nuclear landscape. While the sequence of magic numbers is well established for stable nuclei, evidence reveals modifications for nuclei with a large proton-to-neutron asymmetry. Here, we provide the first spectroscopic study of the doubly magic nucleus $^{78}$Ni, fourteen neutrons beyond the last stable nickel isotope. We provide direct evidence for its doubly magic nature, which is also predicted by ab initio calculations based on chiral effective field theory interactions and the quasi-particle random-phase approximation. However, our results also provide the first indication of the breakdown of the neutron magic number 50 and proton magic number 28 beyond this stronghold, caused by a competing deformed structure. State-of-the-art phenomenological shell-model calculations reproduce this shape coexistence, predicting further a rapid transition from spherical to deformed ground states with $^{78}$Ni as turning point.

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arXiv2018

Testing the capability of low-energy light ions identification of the TRACE silicon detectors

The in-beam tests of two Si pixel type TRACE detectors have been performed at Laboratori Nazionali di Legnaro (Italy). The aim was to investigate the possibility of identifying heavy-ion reactions products with mass A~10 at low kinetic energy, i.e., around 10 MeV. Two separate read-out chains, digital and analog, were used. The Pulse Shape Analysis technique was employed to obtain the identification matrices for the digitally processed part of the data. Separation in both charge and mass was obtained, however, the $α$ particles contaminated significantly the recorded data in the lower energy part. Due to this effect, the identification of the light products ($^{7,6}$Li isotopes) could be possible down only to ~20 MeV

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