208Po populated through EC/β+ decay Brunet, M.; Berry, T.A.; Podolyák, Zs ...
Journal of physics. Conference series,
12/2020, Letnik:
1643, Številka:
1
Journal Article
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The structure of 208Po resulting from the EC/β+ decay of 208At was studied at CERN's ISOLDE Decay Station (IDS). The high statistics afforded by the high yield of 208At and the high efficiency HPGe ...clusters at the IDS allowed for greater insight into lower intensity transitions and thus significant expansion of the 208Po level scheme. Furthermore, investigation into the isomeric state yielded a new half life 377(9) ns in addition to uncovering new transitions populating the state.
The β decays from both the ground state and a long-lived isomer of ^{133}In were studied at the ISOLDE Decay Station (IDS). With a hybrid detection system sensitive to β, γ, and neutron spectroscopy, ...the comparative partial half-lives (logft) have been measured for all their dominant β-decay channels for the first time, including a low-energy Gamow-Teller transition and several first-forbidden (FF) transitions. Uniquely for such a heavy neutron-rich nucleus, their β decays selectively populate only a few isolated neutron unbound states in ^{133}Sn. Precise energy and branching-ratio measurements of those resonances allow us to benchmark β-decay theories at an unprecedented level in this region of the nuclear chart. The results show good agreement with the newly developed large-scale shell model (LSSM) calculations. The experimental findings establish an archetype for the β decay of neutron-rich nuclei southeast of ^{132}Sn and will serve as a guide for future theoretical development aiming to describe accurately the key β decays in the rapid-neutron capture (r-) process.
Neutron-rich Ba isotopes are expected to exhibit octupolar correlations, reaching their maximum in isotopes around mass A = 146. The odd-A neutron-rich members of this isotopic chain show typical ...patterns related to non-axially symmetric shapes, which are however less marked compared to even-A ones, pointing to a major contribution from vibrations. In the present paper we present results from a recent study focused on 148-150Cs β-decay performed at the ISOLDE Decay Station equipped with fast-timing detectors. A detailed analysis of the measured decay half-lives and decay scheme of 149Ba is presented, giving a first insight in the structure of this neutron-rich nucleus.
A multi-particle decay experiment was successfully performed at the ISOLDE Decay Station. In this new permanent station, devoted to beta-decay studies, the novel MAGISOL Si-Plugin Chamber was ...installed to study the exotic decay modes of the proton drip-line nucleus Ar-31. The motivation was to search for beta 3p and beta 3p gamma channels, as well as to provide information on resonances in S-30 and P-29 relevant for the astrophysical rp-process. Description of the experimental set-up and preliminary results are presented.
The ^{12}C(α,γ)^{16}O reaction plays a central role in astrophysics, but its cross section at energies relevant for astrophysical applications is only poorly constrained by laboratory data. The ...reduced α width, γ_{11}, of the bound 1^{-} level in ^{16}O is particularly important to determine the cross section. The magnitude of γ_{11} is determined via sub-Coulomb α-transfer reactions or the β-delayed α decay of ^{16}N, but the latter approach is presently hampered by the lack of sufficiently precise data on the β-decay branching ratios. Here we report improved branching ratios for the bound 1^{-} level b_{β,11}=(5.02±0.10)×10^{-2} and for β-delayed α emission b_{βα}=(1.59±0.06)×10^{-5}. Our value for b_{βα} is 33% larger than previously held, leading to a substantial increase in γ_{11}. Our revised value for γ_{11} is in good agreement with the value obtained in α-transfer studies and the weighted average of the two gives a robust and precise determination of γ_{11}, which provides significantly improved constraints on the ^{12}C(α,γ) cross section in the energy range relevant to hydrostatic He burning.
The structure of $^{34}$Si was studied through $\gamma$ spectroscopy
separately in the $\beta^-$ decays of $^{34}$Mg and $^{34}$Al at the ISOLDE
facility of CERN. Different configurations in ...$^{34}$Si were populated
independently from the two recently identified $\beta$-decaying states in
$^{34}$Al having spin-parity assignments $J^\pi = 4^-$ dominated by the normal
configuration $\pi (d_{5/2})^{-1} \otimes \nu (f_{7/2})$ and $J^\pi = 1^+$ by
the intruder configuration $\pi (d_{5/2})^{-1} \otimes \nu
(d_{3/2})^{-1}(f_{7/2})^{2}$. The paper reports on spectroscopic properties of
$^{34}$Si such as an extended level scheme, spin and parity assignments based
on log($ft$) values and $\gamma$-ray branching ratios, absolute $\beta$ feeding
intensities and neutron emission probabilities. A total of 11 newly identified
levels and 26 transitions were added to the previously known level scheme of
$^{34}$Si. Large scale shell-model calculations using the {\sc sdpf-u-mix}
interaction, able to treat higher order intruder configurations, are compared
with the new results and conclusions are drawn concerning the predictive power
of {\sc sdpf-u-mix}, the $N=20$ shell gap, the level of mixing between normal
and intruder configurations for the 0$_1^+$, 0$_2^+$ and 2$_1^+$ states and the
absence of triaxial deformation in $^{34}$Si.
The structure of \(^{34}\)Si was studied through \(\gamma\) spectroscopy separately in the \(\beta^-\) decays of \(^{34}\)Mg and \(^{34}\)Al at the ISOLDE facility of CERN. Different configurations ...in \(^{34}\)Si were populated independently from the two recently identified \(\beta\)-decaying states in \(^{34}\)Al having spin-parity assignments \(J^\pi = 4^-\) dominated by the normal configuration \(\pi (d_{5/2})^{-1} \otimes \nu (f_{7/2})\) and \(J^\pi = 1^+\) by the intruder configuration \(\pi (d_{5/2})^{-1} \otimes \nu (d_{3/2})^{-1}(f_{7/2})^{2}\). The paper reports on spectroscopic properties of \(^{34}\)Si such as an extended level scheme, spin and parity assignments based on log(\(ft\)) values and \(\gamma\)-ray branching ratios, absolute \(\beta\) feeding intensities and neutron emission probabilities. A total of 11 newly identified levels and 26 transitions were added to the previously known level scheme of \(^{34}\)Si. Large scale shell-model calculations using the {\sc sdpf-u-mix} interaction, able to treat higher order intruder configurations, are compared with the new results and conclusions are drawn concerning the predictive power of {\sc sdpf-u-mix}, the \(N=20\) shell gap, the level of mixing between normal and intruder configurations for the 0\(_1^+\), 0\(_2^+\) and 2\(_1^+\) states and the absence of triaxial deformation in \(^{34}\)Si.
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