The Matter’s Origin from RadioActivity (MORA) experiment laser polarises 23 Mg + ions in a Paul Trap to measure the D correlation in their β-decay. During the experiment, the polarisation degree of the ion cloud is monitored with two silicon detectors at opposite sides from the trap. Here, the sensitivity and the systematic uncertainties of this monitoring are studied using a home-made event generator, PENELOPE, and Geant4.

A high-precision measurement of the electron-capture (EC) decay Q value for the ground-state-to-ground-state (gs-to-gs) transition of ^113Sn to ^113In has been performed using the JYFLTRAP double Penning trap mass spectrometer. Employing the phase-imaging ion-cyclotron-resonance technique, the isomeric state of ^113Sn at 77.389(19) keV was resolved, and the cyclotron frequency ratio measured between the isomer ^113mSn and the daughter nucleus ^113In. This yielded an isomer-to-ground-state Q value of 1116.64(19) keV and gs-to-gs Q value of 1039.25(19) keV. The atomic mass excess of ^113Sn was determined as -88327.87(27) keV/c^2, in excellent agreement with the Atomic Mass Evaluation 2020 (AME2020) but with a sixfold precision improvement. Using nuclear energy-level data for ^113In, we identified two low Q-value transitions of the ground state of ^113Sn to excited states of ^113In at 1024.280(50) keV (Q_EC^* = 14.97(20) keV, second forbidden non-unique) and 1029.650(50) keV (Q_EC^* = 9.60(20) keV, allowed). The allowed transition exhibits small energy differences (Δ_L1 = 5.58(20) keV, Δ_L2 = 5.87(20) keV) from L1 and L2 shell binding energies, enhancing endpoint events. Partial half-lives and energy-release spectra were calculated using the self-consistent Dirac-Hartree-Fock-Slater (DHFS) method (including exchange, overlap, shake-up, and shake-off corrections) together with the nuclear shell model, show enhanced endpoint sensitivity for the allowed transition to the state at 1029.650 keV. Including subthreshold atomic states in the spectral function enhances the EC rate near the zero-neutrino-momentum region by a factor of five, enabling new approaches for low Q-value EC reactions in neutrino-mass studies.

The isomeric yield ratio (IYR) of fission products is an observable that carries relevant information about the fragments emerging from the scission of a fissioning nucleus. We report on IYR of 96,98,100Y and 100,102Nb, together with the previously reported values for 97Y and 99Nb, produced in the 28 MeV α-induced fission of 232Th at the Ion Guide Isotope Separation On-Line (IGISOL) facility of the University of Jyväskylä. We measured the IYR using two different techniques, the phase-imaging ion-cyclotron-resonance (PI-ICR) and the multiple-reflection time-of-flight mass spectrometry (MR-TOF-MS) methods. Moreover, we measured the masses of the long-lived states in 98,100Y and 100,102Nb populated via in-trap β-decay of their precursors. Since the β-decay selectively populates states with a favourable spin-parity, we could identify the measured state and show that the ground state is the low-spin state in the cases of 98Y and 100Nb, while it is the high-spin state in the cases of 100Y and 102Nb. This measurement confirms the spin-parity assignments of all the nuclei as they are reported in the NUBASE2020 evaluations, disagreeing with the assignment for 100Y reported in the ENSDF evaluation.Making also use of previously reported data, we observe an anomalously low IYR for the N=59 isotope 98Y as compared to other yttrium or neighboring niobium isotopes. This behavior is very rare across the nuclear chart and is posited to be connected to the characteristic shape coexistence of 98Y, and to the change in the charge radii of the ground and excited states in the N=58−60 region.

HIBISCUS (Helium-Inflated Beam Improvement Setup that Cools and Undermines Spreads), a new radiofrequency quadrupole cooler-buncher device has been developed and commissioned offline at the Ion Guide Isotope Separator On-Line (IGISOL) facility in Jyväskylä in Finland, as an in-kind contribution for the Facility for Antiproton and Ion Research facility. HIBISCUS improves the ion optical properties of incident low-energy 6 keV beams with the option to have it ultimately extracted in temporally short bunches (<1 μs). This paper provides technical descriptions of its main characteristics, along with a set of optimum working parameters and performance in terms of transmission efficiency, longitudinal energy spread of the cooled ions and temporal width of the extracted bunches.

Anew linear Paul trap section has been constructed to replace the existing bunching section of the radiofrequency quadrupole (RFQ) cooler-buncher at the IGISOL radioactive ion beam facility. The coolerbuncher is used to transform a continuous ion beam to temporally short bursts of ions. The new miniaturised cooler-buncher section produces significantly shorter bunches in time, required by the new Multi-Reflection Time-of-Flight Mass Spectrometer. In this article, we report on the longitudinal properties of the ion bunches and compare the results to an analytical model derived for axial distributions of ions confined in a harmonic trap at thermodynamical equilibrium with a heat bath. The new buncher configuration delivers < 75 ns full-width at half-maximum bunches with a longitudinal emittance of 200 eVns. The bunches have a full- width at half-maximum energy spread of 10 eV. Total transmission efficiency of 45%-65% has been measured from the isotope separator focal plane through the RFQ cooler-buncher, Multi-Reflection Time-of-Flight Mass Spectrometer and JYFLTRAP double Penning trap.

We report on mass measurements of three long-lived states in 114Rh performed with the JYFLTRAP Penning-trap mass spectrometer: the ground state and two isomers with estimated half-lives of about one second. The used Phase-Imaging Ion-Cyclotron-Resonance technique allowed for the discovery of a so far unknown second longlived isomer. All three states were produced directly in proton-induced fission on a uranium target, whereas only the isomeric states were populated in the beta decay of the 114Ru ground state with spin-parity 0+. We propose spin-parity assignments of (6-) for the ground state, and (3+) and (0-) for the isomers. They resolve the puzzle of anomalous fission yields of this isotope despite the existing literature assigning a low angular momentum to the ground state. The experimental evidence is further supported by a detailed analysis based on mean-field calculations with the BSkG3 model. As for many other nuclei in this mass region, considering triaxial shapes is decisive for the interpretation of low-lying states of this nucleus. The discovery of a new isomer in 114Rh and our theoretical work challenge the currently adopted spin-parity assignments in this and several other odd-odd neutron-rich Rh isotopes.

The masses of the ground and isomeric states in 124,125Ag have been measured using the phase-imaging ioncyclotron-resonance technique at the JYFLTRAP double Penning trap mass spectrometer. The ground states of 124Ag and 125Ag were found to be 30(250) keV and 250(430) keV less bound but 36 and 110 times more precise than in the Atomic Mass Evaluation 2020, respectively. The excitation energy of 124Agm, Ex = 188.2(25) keV, was determined for the first time. The new precise mass values have been utilized to study the evolution of nuclear structure via two-neutron separation energies. The impact on the astrophysical rapid neutron capture process has been investigated via neutron-capture reaction rate calculations. The precision measurements indicate a more linear trend in two-neutron separation energies and reduce the mass-related uncertainties for the neutron-capture rate of 124Ag(n, gamma ) 125Ag by a factor of around 100. The new mass values also improve the mass of 123Pd, previously measured using 124Ag as a reference.

The origin of the large angular momenta observed for fission fragments is still a question under discussion. To address this, we study isomeric yield ratios (IYRs), i.e., the relative population of two or more long-lived metastable states with different spins, of fission products. We report on IYRs of 17 isotopes produced in the 28-MeV alpha-induced fission of Th-232 at the IGISOL facility of the University of Jyvaskyla. The fissioning nuclei in this reaction are U-233,U-234,U-235*. We compare our data to IYRs from thermal neutron-induced fission of U-233 and U-235, and we observe statistically significant larger IYRs in the Th-232(alpha, f) reaction, where the average compound nucleus (CN) spin is 7.7 h, than in U-233,U-235(n(th), f), with average spins of 2.6 and 3.6 h, respectively. To assess the influence of the excitation energy, we study literature data of IYRs from photon-induced fission reactions, and find that, within current uncertainties, the IYRs indicate no dependency of the CN excitation energy. We conclude that the different IYRs seem to be due to the different CN spins alone. This would imply that the fission fragment angular momentum only partly comes from the fission process itself and is, in addition, influenced by the angular momentum present in the CN.

We report on high-precision atomic mass measurements of ^{148-153}La and ^{151}Ce performed with the JYFLTRAP double Penning trap using the phase-imaging ion-cyclotron-resonance technique. The masses of ^{152,153}La were experimentally determined for the first time. We confirm the sharp kink in the two-neutron separation energies at the neutron number N=93 in the cerium (Z=58) isotopic chain. Our precision mass measurements of the most exotic neutron-rich lanthanum (Z=57) isotopes reveal a unexpected sudden increase in two-neutron separation energies from N=92 to N=93. Unlike in the cerium isotopic chain, the kink is not sharp but extends to N=94 forming a prominent bump. The gain in energy is about 0.4 MeV, making it one of the strongest changes in two-neutron separation energies over the whole chart of nuclides, away from nuclear shell closures. The results, correlated with a predicted onset of quadrupole deformation for N≥92, call for further studies to elucidate the structure of neutron-rich lanthanum isotopes.

A direct measurement of the ground-state-to-ground-state electron-capture decay Q (QEC) value of 97Tc has been conducted employing the high-resolving-power phase-imaging ion-cyclotron-resonance technique with the double Penning trap mass spectrometer JYFLTRAP. The resulting QEC value for 97Tc is 324.82(21) keV, exhibiting a precision approximately 19 times higher than the value adopted in the newest Atomic Mass Evaluation (AME2020) and differing by 1.2 sigma. Furthermore, by combining this refined Q value with nuclear energy-level data for the decay-daughter 97Mo, a potential ultralow Q-value transition 97Tc (9/2+, ground state) -> 97Mo & lowast; [320(1) keV] was detected. The ground-state-to-excited-state electron-capture decay Q value (Q & lowast;EC) of this transition was determined to be 4.8(10) keV, confirming it to be energetically allowed with a confidence level of exceeding 4 sigma. The captures of electrons occupying the L and higher shells for this transition are energetically allowed, giving a value of 2.0(10) keV for the closest distance of Q & lowast; EC to the allowed binding energy of the L1 shell. To predict partial half-lives and energy-release distributions for this transition, the atomic self-consistent many-electron Dirac-Hartree-Fock-Slater method and the nuclear shell model have been employed. Dominant correction terms such as exchange and overlap corrections, as well as shake-up and shake-off effects, were included in the final results. Moreover, in the case of a possible allowed transition, the normalized distribution of released energy in the electron-capture decay of 97Tc to the excited 320-keV state of 97Mo, is compared with that of 163Ho, which is being used for electron-neutrino-mass determination. A pseudoexperiment technique was introduced to calculate error propagation in half-life and the 68% confidence interval for normalized energy distributions.

The Q value of the double-beta ( β ^-β ^- ) decay of ^104 Ru ( Q_β ^-β ^- -value) was determined using the JYFLTRAP double Penning trap mass spectrometer employing the Phase-Imaging Ion Cyclotron Resonance (PI-ICR) method. The obtained value of 1297.705(36) keV is in agreement with the current literature value of 1299.4(27) keV but is over 70 times more precise. As a consistency check on a 100 eV level, we also measured the precisely known ^102 Pd double-electron capture Q value, Q_ECEC=1203.531(92) keV, which agrees with the literature value of 1203.47(4) keV. The measured Q value of ^104 Ru β ^-β ^- decay was used in calculations of the phase-space factors of the double-beta decay. Also, the nuclear matrix elements were calculated using the microscopic interacting boson model (IBM-2) as a nuclear model and compared with other available results. With these theoretical calculations based on the measured Q value, the estimates for the two-neutrino and neutrinoless double-beta decay half-lives of ^104 Ru were calculated to be t_1/2^2νββ>5.449× 10^21 years and t_1/2^0νββ>5.775× 10^26 years, respectively. The calculated 2νβ ^-β ^- half-life is longer than the current experimental lower limit but short enough to be potentially within reach with future high precision experiments.

We have determined the decay energy ( Q value) of the double beta decay of $$^{122}$$ 122 Sn with the JYFLTRAP double Penning trap mass spectrometer using the Phase-Imaging Ion Cyclotron Resonance technique. Our new Q value, 373.58(12) keV, agrees with the literature value but is 20 times more precise. We also measured the Q value for the double beta decay of $$^{124}$$ 124 Sn with unprecedented precision, 2293.542(83) keV. The Q values of $$^{122}$$ 122 Sn and $$^{124}$$ 124 Sn were used to calculate precisely the phase-space factors for the neutrinoless double beta ( $$0\nu \beta \beta $$ 0 ν β β ) decay mode of these nuclei. With the phase-space factor and our computed nuclear matrix elements (NMEs) we predict the $$0\nu \beta \beta $$ 0 ν β β -decay half-life of $$^{122}$$ 122 Sn based on the recently extracted upper limit of the effective neutrino mass by the KamLAND-Zen experiment. We used three nuclear-structure frameworks to compute the NMEs, namely the proton-neutron quasiparticle random-phase approximation (pnQRPA), the microscopic interacting boson model (IBM-2), and a hybrid model exploiting both the pnQRPA and the nuclear shell model (NSM). We find that including the short-range components enhances the total NME in the IBM-2 model, making it significantly larger than the NMEs calculated with the pnQRPA and hybrid models. Nevertheless, for all models, the obtained half-lives are very long for $$^{122}$$ 122 Sn ( $$\approx 10^{27}$$ ≈ 10 27 – $$10^{29}$$ 10 29 years), making the observation of $$0\nu \beta \beta $$ 0 ν β β decay of $$^{122}$$ 122 Sn experimentally challenging. On the other hand, the hybrid-model calculated value of the NME for $$^{124}$$ 124 Sn goes, interestingly enough, toward those previously computed by the NSM and the ab initio model.

We report on the masses and hyperfine structure of ground and isomeric states in ^114,116,118,120Ag isotopes, measured with the phase-imaging ion-cyclotron-resonance technique (PI-ICR) with the JYFLTRAP mass spectrometer and the collinear laser spectroscopy beamline at the Ion Guide Isotope Separator On-Line (IGISOL) facility, Jyväskylä, Finland. We measured the masses and excitation energies, electromagnetic moments, and charge radii, and firmly established the nuclear spins of the long-lived states. A new isomer was discovered in ^118Ag and the half-lives of ^118Ag long-lived states were reevaluated. We unambiguously pinned down the level ordering of all long-lived states, placing the inversion of the I = 0^- and I = 4^+ states at A = 118 (N = 71). Lastly, we compared the electromagnetic moments of each state to empirical single-particle moments to identify the dominant configuration where possible.

We report on new precision mass measurements of neutron-rich $^{137}$Sb and $^{136-142}$I isotopes from the JYFLTRAP double Penning trap mass spectrometer. We confirm the value from the previous Penning-trap measurement of $^{137}$Sb at the Canadian Penning Trap and therefore rule out the conflicting result from the Experimental Storage Ring. The ground state and isomer in $^{136}$I were resolved and measured directly for the first time. The isomer excitation energy, $E_x = 215.1(43)$ keV, agrees with the literature but is three times more precise. The measurements have improved the precision of the mass values and confirmed previous results in the majority of cases. However, for $^{138,140}$I the results differ by 17(6) keV and 23(12) keV, respectively. This could be explained by an unresolved contamination or different ratio of unresolved isomeric states in the case of $^{140}$I.

High-precision mass measurements of exotic ^{95-97}Ag isotopes close to the N=Z line have been conducted with the JYFLTRAP double Penning trap mass spectrometer, with the silver ions produced using the recently commissioned inductively heated hot cavity catcher laser ion source at the Ion Guide Isotope Separator On-Line facility. The atomic mass of ^{95}Ag was directly determined for the first time. In addition, the atomic masses of β-decaying 2^{+} and 8^{+} states in ^{96}Ag have been identified and measured for the first time, and the precision of the ^{97}Ag mass has been improved. The newly measured masses, with a precision of ≈1  keV/c^{2}, have been used to investigate the N=50 neutron shell closure, confirming it to be robust. Empirical shell-gap and pairing energies determined with the new ground-state mass data are compared with the state-of-the-art ab initio calculations with various chiral effective field theory Hamiltonians. The precise determination of the excitation energy of the ^{96m}Ag isomer in particular serves as a benchmark for ab initio predictions of nuclear properties beyond the ground state, specifically for odd-odd nuclei situated in proximity to the proton dripline below ^{100}Sn. In addition, density functional theory calculations and configuration-interaction shell-model calculations are compared with the experimental results. All theoretical approaches face challenges to reproduce the trend of nuclear ground-state properties in the silver isotopic chain across the N=50 neutron shell and toward the proton dripline.

We report on a set of high-precision measurements of nuclear binding and excitation energies, as well as nuclear spins, magnetic dipole and electric quadrupole moments of neutron-rich silver isotopes, 113−123Ag. The measurements were performed using the JYFLTRAP mass spectrometer and the collinear laser spectroscopy beamline at the Ion Guide Isotope Separator On-Line (IGISOL) facility. For the first time, we can firmly establish the ordering of the long-lived Iπ=1/2−,7/2+ states in these isotopes, and pin down the inversion of these two levels at either A=121(N=74) or A=123(N=76). We compare these findings to calculations performed with density functional theory (DFT), from which we establish the crucial role that the spin-orbit strength and time-odd mean fields play in the simultaneous description of electromagnetic moments and nuclear binding.

Precision mass measurements of 104Y, 106Zr, 104,104m,109Nb, and 111,112Mo have been performed with the JYFLTRAP double Penning trap mass spectrometer at the Ion Guide Isotope Separator On-Line facility. The order of the long-lived states in 104Nb was unambiguously established. The trend in two-neutron separation energies around the N=66 neutron midshell appeared to be steeper with respect to the Atomic Mass Evaluation 2020 extrapolations for the 39Y and 40Zr isotopic chains and less steep for the 41Nb chain, indicating a possible gap opening around Z=40. The experimental results were compared to the BSkG2 model calculations performed with and without vibrational and rotational corrections. All of them predict two low-lying minima for 106Zr. While the unaltered BSkG2 model fails to predict the trend in two-neutron separation energies, selecting the more deformed minima in calculations and removing the vibrational correction, the calculations are more in line with experimental data. The same is also true for the 21+ excitation energies and differences in charge radii in the Zr isotopes. The results stress the importance of improved treatment of collective corrections in large-scale models and further development of beyond-mean-field techniques.

A new isomeric (4^-) state at 285.5(32) keV in ^162Tb was reported by R. Orford et al. [Phys. Rev. C 102, 011303(R) (2020)] based on a Penning-trap mass measurement. Here we show that this result is not compatible with existing experimental data. The state identified as ^162Tb^m with a mass-excess value of -65593.9(25) keV is actually the 1^- ground state. The state identified as the ground state of ^162Tb is most likely a molecular contaminant with the same mass-over-charge ratio.

The excited structure of the single-hole nucleus 131 Sn populated by the beta - decay of 131 In was investigated in detail at the ISOLDE facility at CERN. This new experiment took advantage of isomeric purification capabilities provided by resonant ionization, making it possible to independently study the decay of each isomer for the first time. The position of the first-excited nu h 11 / 2 neutron-hole state was confirmed via an independent mass spectroscopy experiment performed at the Ion Guide Isotope Separator On-Line facility at the University of Jyv & auml;skyl & auml;. The level scheme of 131 Sn was notably expanded with the addition of 31 new gamma-ray transitions and 22 new excited levels. The gamma-emitting excited levels above the neutron separation energy in 131 Sn were investigated, revealing a large number of states, which in some cases decay by transitions to other neutron-unbound states. Our analysis showed the dependence between the population of these states in 131 Sn and the beta-decaying 131 In state feeding them. Profiting from the isomer selectivity, it was possible to estimate the direct beta feeding to the 3/2+ / 2 + ground and 11/2- / 2 - isomeric states, disentangling the contributions from the three indium parent states. This made possible to resolve the discrepancies in log ft for first-forbidden transitions observed in previous studies, and to determine the beta-delayed neutron decay probability (Pn) P n ) values of each indium isomers independently. The first measurement of subnanosecond lifetimes in 131 Sn was performed in this work. A short T 1 / 2 = 18(4)-ps value was measured for the 1/2+ / 2 + neutron single-hole 332-keV state, which indicates an enhanced l-forbidden M 1 behavior for the nu 3 s - 1 1/2 / 2 -> nu 3 d - 13 / 2 transition. The measured half-lives of high-energy states populated in the beta decay of the (21/2+) / 2 + ) second isomeric state ( 131 m 2 In) provided valuable information on transition rates, supporting the interpretation of these levels as core-excited states analogous to those observed in the doubly-magic 132 Sn.

We report on the precise mass measurements of the ^91 Sr and ^95 Y isotopes performed using the JYFLTRAP double Penning trap mass spectrometer. The mass-excess values from this work, ME(^91Sr) = -83645.5(13) keV and ME(^95Y) = -81226.4(10) keV, deviate by 6.5(52) keV and -18(7) keV from the Atomic Mass Evaluation 2020 (AME20). In the case of ^91 Sr the new result disagrees with the ISOLTRAP value, while for ^95 Y, it agrees with the older JYFLTRAP value.