Search results for "decays"

Excited states in 217Ra populated in the α decay of 221Th

2020

Fine structure in the α decay of 22190Th, populating excited states in 21788Ra, was studied using αγ-coincidence spectroscopy. Two α-decay branches from 221Th have been newly observed, with Eα(keV)[bα(%)]=7951(8)[0.14(3)] and 8247(3)[1.51(12)], together with three previously known branches. Also, two new states in 217Ra were identified at E = 177 and 227 keV. The ground-state configurations of the odd-A, N = 131 transitional isotones above 208Pb are interpreted from their α-decay fine structure systematics and considered in terms of predictions using spherical shell and reflection-asymmetric models. peerReviewed

α-spectroscopy studies of the new nuclides 165Pt and 170Hg

2019

The new nuclides 165Pt and 170Hg were produced in the reactions 92Mo(78Kr,5n) and 96Ru(78Kr,4n) at bombarding energies of 418 MeV and 390 MeV, respectively. For 170Hg an α-particle energy of Eα=7590(30)keV and half-life of t1/2=0.08+0.40−0.04ms were deduced, while for 165Pt the corresponding values were 7272(14) keV and 0.26+0.26−0.09ms. Comparison of the reduced α-decay widths with systematics indicates that both α decays are unhindered. Although combining the measured α-decay Q values with extrapolated masses suggests that both new nuclides are unbound to two-proton emission by more than 1 MeV, their α-decay half-lives are too short for this decay mode to compete. Improved data were also …

First determination of β-delayed multiple neutron emission beyond A = 100 through direct neutron measurement : The P2n value of 136Sb

2018

Background: β-delayed multiple neutron emission has been observed for some nuclei with A≤100, being the Rb100 the heaviest β2n emitter measured to date. So far, only 25P2n values have been determined for the ≈300 nuclei that may decay in this way. Accordingly, it is of interest to measure P2n values for the other possible multiple neutron emitters throughout the chart of the nuclides. It is of particular interest to make such a measurement for nuclei with A>100 to test the predictions of theoretical models and simulation tools for the decays of heavy nuclei in the region of very neutron-rich nuclei. In addition, the decay properties of these nuclei are fundamental for the understanding of a…

Second-forbidden nonunique β− decays of 24Na and 36Cl assessed by the nuclear shell model

2020

We have performed a systematic study of the log f t values, shape factors, and electron spectra for the second-forbidden nonunique β− decays of 24Na(4+) →24Mg(2+) and 36Cl(2+) →36Ar(0+) transitions under the framework of the nuclear shell model. We have performed the shell model calculations in the sd model space, using more recent microscopic effective interactions such as Daejeon16, chiral N3LO, and JISP16. These interactions are derived from the no-core shell model wave functions using Okubo-Lee-Suzuki transformation. For comparison, we have also shown the results obtain from the phenomenological USDB interaction. To test the predictive power of these interactions first we have computed …

Total absorption γ-ray spectroscopy of the β decays of 96gs,mY

2022

The β decays of the ground state (gs) and isomeric state (m) of 96Y have been studied with the total absorption γ-ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility. The separation of the 8+ isomeric state from the 0− ground state was achieved thanks to the purification capabilities of the JYFLTRAP double Penning trap system. The β-intensity distributions of both decays have been independently determined. In the analyses the deexcitation of the 1581.6 keV level in 96Zr, in which conversion electron emission competes with pair production, has been carefully considered and found to have significant impact on the β-detector efficiency, influencing the β-intensity di…

Searches for lepton number violating $K^+$ decays

2019

The NA62 experiment at CERN reports a search for the lepton number violating decays K+ -> pi(-)e(+)e(+) and K+ -> pi(-)mu(+)mu(+) using a data sample collected in 2017. No signals are observed, and upper limits on the branching fractions of these decays of 2.2 x 10(-10) and 4.2 x 10(-11) are obtained, respectively, at 90% confidence level. These upper limits improve on previously reported measurements by factors of 3 and 2, respectively.

Beta-spectrum shapes of forbidden β decays

2018

The neutrinoless [Formula: see text] decay of atomic nuclei continues to attract fervent interest due to its potential to confirm the possible Majorana nature of the neutrino, and thus the nonconservation of the lepton number. At the same time, the direct dark matter experiments are looking for weakly interacting massive particles (WIMPs) through their scattering on nuclei. The neutrino-oscillation experiments on reactor antineutrinos base their analyses on speculations of [Formula: see text]-spectrum shapes of nuclear decays, thus leading to the notorious “reactor antineutrino anomaly.” In all these experimental efforts, one encounters the problem of [Formula: see text]-spectrum shapes of…

Neutrino-nuclear responses for astro-neutrinos, single beta decays and double beta decays

2019

Neutrino–nuclear responses associated with astro-neutrinos, single beta decays and double beta decays are crucial in studies of neutrino properties of interest for astro-particle physics. The present report reviews briefly recent studies of the neutrino–nuclear responses from both experimental and theoretical points of view in order to obtain a consistent understanding of the many facets of the neutrino–nuclear responses. Subjects discussed in this review include (i) experimental studies of neutrino–nuclear responses by means of single beta decays, charge-exchange nuclear reactions, muon- photon- and neutrino–nuclear reactions, and nucleon-transfer reactions, (ii) implications of and discus…

Value of the Axial-Vector Coupling Strength in β and ββ Decays : A Review

2017

Restoring the valence-shell stabilization in 140Nd

2020

A projectile Coulomb-excitation experiment was performed at the radioactive-ion beam facility HIE-ISOLDE at CERN to obtain $E2$ and $M1$ transition matrix elements of $^{140}$Nd using the multistep Coulomb-excitation code GOSIA. The absolute $M1$ strengths, $\textrm{B}(M1;2^+_2→2^+_1)=0.033(8)μ^2_N,\textrm{B}(M1;2^+_3→2^+_1)=0.26^{+0.11}_{−0.10}μ^2_N$, and $\textrm{B}(M1;2^+_4→2^+_1)<0.04μ^2_{\textrm{N}}$, identify the $2^+_3$ state as the main fragment of the one-quadrupole-phonon proton-neutron mixed-symmetry state of $^{140}$Nd. The degree of F-spin mixing in $^{140}$Nd was quantified with the determination of the mixing matrix element $V_{\textrm{F−mix}}<7^{+13}_{−7}$keV.