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A precise determination of the ground state $^{111}$In ($9/2^+$) electron capture to ground state of $^{111}$Cd ($1/2^+$) $Q$ value has been performed utilizing the double Penning trap mass spectrometer, JYFLTRAP. A value of 857.63(17) keV was obtained, which is nearly a factor of 20 more precise than the value extracted from the Atomic Mass Evaluation 2020 (AME2020). The high-precision electron-capture $Q$ value measurement along with the nuclear energy level data of 866.60(6) keV, 864.8(3) keV, 855.6(10) keV, and 853.94(7) keV for $^{111}$Cd was used to determine whether the four states are energetically allowed for a potential ultra-low $Q$-value $\beta^{}$ decay or electron-capture decay. Our results confirm that the excited states of 866.60(6) keV with spin-parity ($J^\pi$) of 3/2$^{+}$ and 864.8(3) keV with $J^\pi$ = 3/2$^{+}$ are ruled out due to their deduced electron-capture $Q$ value being smaller than 0 keV at the level of around 20$\sigma$ and 50$\sigma$, respectively. Electron-capture decays to the excited states at 853.94(7) keV ($J^\pi$ = 7/2$^+$) and 855.6(10) keV ($J^\pi$ = 3/2$^+$), are energetically allowed with $Q$ values of 3.69(19) keV and 2.0(10) keV, respectively. The allowed decay transition $^{111}$In (9/2$^{+}$) $\rightarrow$ $^{111}$Cd (7/2$^{+}$), with a $Q$ value of 3.69(19) keV, is a potential a new candidate for neutrino-mass measurements by future EC experiments featuring new powerful detection technologies. The results show that the indium level $2p_{1/2}$ for this decay branch leads to a significant increase in the number of EC events in the energy region sensitive to the electron neutrino mass., Comment: 12 pages, 4 figures

Collinear laser spectroscopy of the N=Z=21 self-conjugate nucleus 42Sc has been performed at the JYFL IGISOL IV facility in order to determine the change in nuclear mean-square charge radius between the Iπ=0+ ground state and the Iπ=7+ isomer via the measurement of the 42g,42mSc isomer shift. New multi-configurational Dirac-Fock calculations for the atomic mass shift and field shift factors have enabled a recalibration of the charge radii of the 42−46Sc isotopes which were measured previously. While consistent with the treatment of proton-neutron, proton-proton and neutron-neutron pairing on an equal footing, the reduction in size for the isomer is observed to be of a significantly larger magnitude than that expected from both shell-model and ab-initio calculations. The measured nuclear magnetic dipole moment and electric quadruple moment, on the other hand, are in good agreement with simple empirical estimates and shell-model calculations. Collinear laser spectroscopy of the $N=Z=21$ self-conjugate nucleus $^{42}$Sc has been performed at the JYFL IGISOL IV facility in order to determine the change in nuclear mean-square charge radius between the $I^{\pi}=0^{+}$ ground state and the $I^{\pi}=7^{+}$ isomer via the measurement of the $^{42\mathrm{g},42\mathrm{m}}$Sc isomer shift. New multi-configurational Dirac-Fock calculations for the atomic mass shift and field shift factors have enabled a recalibration of the charge radii of the $^{42-46}$Sc isotopes which were measured previously. While consistent with the treatment of proton-neutron, proton-proton and neutron-neutron pairing on an equal footing, the reduction in size for the isomer is observed to be of a significantly larger magnitude than that expected from both shell model and ab-initio calculations.

Isomeric states in 128In and 130In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing state-of-the-art ion manipulation techniques, three different beta-decaying states in 128In and 130In have been separated and their masses measured. JYFLTRAP was also used to select the ions of interest for identification at a post-trap decay spectroscopy station. A new beta-decaying high-spin isomer feeding the isomer in 128Sn has been discovered in 128In at 1797.6(20) keV. Shell-model calculations employing a CD-Bonn potential re-normalized with the perturbative G-matrix approach suggest this new isomer to be a 16⁺ spin-trap isomer. In 130In, the lowest-lying (10⁻) isomeric state at 58.6(82) keV was resolved for the first time using the phase-imaging ion cyclotron resonance technique. The energy difference between the 10⁻ and 1⁻ states in 130In, stemming from parallel/antiparallel coupling of (π0g-19/2) ⊗ (v0h-111/2), has been found to be around 200 keV lower than predicted by the shell model. Precise information on the energies of the excited states determined in this work is crucial for producing new improved effective interactions for the nuclear shell model description of nuclei near 132Sn.

The Q values of the 116Cd and 130Te double-beta decaying nuclei were determined by using a Penning trap mass spectrometer. The new atomic mass difference between 116Cd and 116Sn of 2813.50(13) keV differs by 4.5 keV and is 30 times more precise than the previous value of 2809(4) keV. The new value for 130Te, 2526.97(23) keV is close to the Canadian Penning trap value of 2527.01 ± 0.32 keV (Scielzo et al., 2009) [1] , but differs from the Florida State University trap value of 2527.518 ± 0.013 keV (Redshaw et al., 2009) [2] by 0.55 keV (2σ). These values are sufficiently precise for ongoing neutrinoless double-beta decay searches in 116Cd and 130Te. Hence, our Q values were used to compute accurate phase-space integrals for these double-beta decay nuclei. In addition, experimental two-neutrino double-beta decay nuclear matrix elements were determined and compared with the theoretical values. The neutrinoless double-beta decay half-lives for these nuclei were estimated using our precise phase-space integrals and considering the range of the best available matrix elements values.

The Q value of the neutrinoless double-electron-capture ( 0 ν ECEC ) decay of 74Se was measured by using the JYFLTRAP Penning trap. The determined value is 1209.169(49) keV, which practically excludes the possibility of a complete energy degeneracy with the second 2 + state (1204.205(7) keV) of 74Ge in a resonant 0 ν ECEC decay. We have also computed the associated nuclear matrix element by using a microscopic nuclear model with realistic two-nucleon interactions. The computed matrix element is found to be quite small. The failure of the resonant condition, combined with the small nuclear matrix element and needed p-wave capture, suppresses the decay rate strongly and thus excludes 74Se as a possible candidate to search for resonant 0 ν ECEC processes.

Radioisotopes of molybdenum have been studied using laser spectroscopy techniques at the IGISOL facility, University of Jyvaskyla. Differences in nuclear charge radii have been determined for neutron deficient isotopes 90,91Mo and neutron rich isotopes 102–106,108Mo (and all stable isotopes). A smooth transition in the mean square charge radii is observed as the neutron number increases with no sudden shape change observed in the region around N = 60 . As N increases, the nuclear deformation appears to go beyond a maximum and a fall off at N = 66 is observed. The magnetic moments of the odd isotopes 91,103,105Mo are also determined.

Penning trap measurements using mixed beams of 76Ge–76Se and 100Mo–100Ru have been utilized to determine the double-beta decay Q-values of 76Ge and 100Mo with uncertainties less than 200 eV. The value for 76Ge, 2039.04(16) keV is in agreement with the published SMILETRAP value, 2039.006(50) keV. The new value for 100Mo, 3034.40(17) keV is 30 times more precise than the previous literature value, sufficient for the ongoing neutrinoless double-beta decay searches in 100Mo. Moreover, the precise Q-value is used to calculate the phase-space integrals and the experimental nuclear matrix element of double-beta decay.

We report changes in mean-square charge radii, δ 〈 r 2 〉 , magnetic moments and quadrupole moments for three multi-quasi particle isomers; 97m2Y, 176mYb and 178m1Hf. All the isomers are observed to display a decrease in 〈 r 2 〉 compared to the lower-lying nuclear state on which the isomer is built. The decreases in 〈 r 2 〉 occur despite the isomers showing increases in quadrupole moment. Possible mechanisms for the effect, which is now seen for six multi-quasi particle isomers, are discussed.

The static moments and isomer shift of the J π = K π =8 − isomeric state in 130 56 Ba have been measured using the technique of collinear laser spectroscopy. The isomer has been found to have a magnetic dipole moment of −0.043(28) μ N and a static quadrupole moment of +2.77(30) b. These values have been used to assign the state as a two neutron 7 2 + [404]⊗ 9 2 − [514] configuration corresponding to a prolate shape. The half-life of the isomer has been confirmed as 9.54(14) ms. The change in the mean square charge radius was found to be 〈 r 2 〉 130m −〈 r 2 〉 130g–s =−0.0473(30) fm 2 .

The magnitude of the Coulomb mixing parameter δ 1 has been experimentally deduced, for the first time, for the β decay of 74 Rb. The estimated magnitude is derived from the feeding of the non-analog first excited 0 + state in 74 Kr. The inferred upper limit of 0.07% is small compared to theoretical predictions. The half-life was measured to be 64.90(9) ms.  2001 Published by Elsevier Science B.V.

Beta decay of 23 Al to excited states in 23 Mg has been studied using low-energy proton and high-energy gamma-ray detection combined with ion-guide-based on-line mass separation. For the first time, a T =3/2 isobaric analogue state, at 7801(2) keV, was observed to decay by both proton and gamma emission, with a proton branching of 0.17(8)%. The deduced resonance strength ωγ =2.2(10) meV is in agreement with upper limits reported from 22 Na(p, γ ) reaction studies. Shell-model calculations are incorporated.

The beta-delayed proton emission from the lightest Ar-isotopes has been recorded with a high-granularity, large solid-angle Si-detector set-up. Proton energy shifts due to beta-recoil have been measured. We demonstrate how this allows the spin of 31 Ar to be determined as 5/2. The method can be applied at decay rates as low as 1 s −1 .

The β-decay of the T z =− 5 2 nucleus 35 Ca was studied at the LISE3 spectrometer at GANIL. The 35 Ca decay scheme was deduced from its β-delayed proton emission into the ground and excited states of 34 Ar and from its β-delayed two-proton emission. The 35 Ca half-life was determined to be 25.7±0.2 ms. The measured transition strength function B(GT) is compared to results obtained from large-scale sd-shell model calculations.

Beta-decay gross properties of neutron-rich isotopes 104Y and 112,113,114Tc produced in 25 MeV proton-induced fission of 238U have been measured. Decays of 104Y with a half-life of 180±60 ms and of 114Tc with a half-life of 150±30 ms are reported for the first time. Beta-delayed neutron emission probabilities of 112,113,114Tc are determined as (1.5±0.2)%, (2.1±0.3)% and (1.3±0.4)%, respectively. Comparison of the observed Pn values with a recent theoretical calculation based on deformed quasiparticle random phase approximation (QRPA) shows good overall agreement for Tc isotopes. However, comparison of beta-decay half-lives of neutron-rich isotopes of Y to Rh with the QRPA model and the refined gross theory shows only modest agreement, pointing to inadequate treatment of structure of these very neutron-rich nuclei lying in a region of rapidly changing deformation.

Beta-decay studies of proton-rich isotopes near the doubly closed-shell nucleus 56Ni are of interest as (i) nuclei with a few nucleons outside a doubly-magic core are expected to represent comparatively simple configurations and thus be useful for testing nuclear shell-model predictions, and (ii) the large decay-energy window guarantees that a sizeable fraction of the strength of the allowed β-decay can be reached by the experiment. Moreover, nuclear structure properties of proton-rich N ~ Z isotopes are of astrophysical interest, e.g., concerning the EC cooling of supernovae and the astrophysical rp-process.

The yields of neutron-rich Ni, Cu, Zn, Ga and Ge-isotopes were measured in 25 MeV proton induced fission of 238 U using the ion guide-based isotope separator technique. The results indicate enhancement for superasymmetric mass division at intermediate excitation energy of the fissioning nucleus and show the potential of this reaction for the production of neutron-rich exotic nuclei around Z = 28.

The double-electron-capture Q value for the 136Ce decay to 136Ba has been determined at JYFLTRAP. The measured value 2378.53(27) keV excludes the energy degeneracy with the 0 + excited state of the decay daughter 136Ba at 2315.32(7) keV in a resonant 0 ν ECEC decay by 11.67 keV. The new Q value differs from the old adopted value 2419(13) keV (Atomic Mass Evaluation 2003) by 40 keV and is 50 times more precise. Our calculations show that the precise Q value renders the resonant 0 ν ECEC decay of 136Ce undetectable by the future underground detectors. We measured also the double-β decay Q value of 136Xe to be 2457.86(48) keV which agrees well with the value 2457.83(37) keV measured at the Florida State University.

The first optical study of the N = 28 shell closure in manganese is reported. Mean-square charge radii and quadrupole moments, obtained for ground and isomeric states in 50–56 Mn, are extracted using new calculations of atomic factors. The charge radii show a well defined shell closure at the magic number. The behaviour of the charge radii is strikingly different to that of the neutron separation energies where no shell effect can be observed. The nuclear parameters can be successfully described by large scale shell model calculations using the GXPF1A interaction.