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The astrophysical $^{25}\mathrm{Al}(p,\ensuremath{\gamma})\phantom{\rule{0.16em}{0ex}}^{26}\mathrm{Si}$ reaction represents one of the key remaining uncertainties in accurately modeling the abundance of radiogenic $^{26}\mathrm{Al}$ ejected from classical novae. Specifically, the strengths of key proton-unbound resonances in $^{26}\mathrm{Si}$, that govern the rate of the $^{25}\mathrm{Al}(p,\ensuremath{\gamma})$ reaction under explosive astrophysical conditions, remain unsettled. Here, we present a detailed spectroscopy study of the $^{26}\mathrm{Si}$ mirror nucleus $^{26}\mathrm{Mg}$. We have measured the lifetime of the ${3}^{+}$, 6.125-MeV state in $^{26}\mathrm{Mg}$ to be $19(3)\phantom{\rule{0.28em}{0ex}}\mathrm{fs}$ and provide compelling evidence for the existence of a ${1}^{\ensuremath{-}}$ state in the $T=1,\phantom{\rule{0.28em}{0ex}}A=26$ system, indicating a previously unaccounted for $\ensuremath{\ell}=1$ resonance in the $^{25}\mathrm{Al}(p,\ensuremath{\gamma})$ reaction. Using the presently measured lifetime, together with the assumption that the likely ${1}^{\ensuremath{-}}$ state corresponds to a resonance in the $^{25}\mathrm{Al}+p$ system at 435.7(53) keV, we find considerable differences in the $^{25}\mathrm{Al}(p,\ensuremath{\gamma})$ reaction rate compared to previous works. Based on current nova models, we estimate that classical novae may be responsible for up to $\ensuremath{\approx}15%$ of the observed galactic abundance of $^{26}\mathrm{Al}$.

We report the first direct determination of the ground-state to ground-state electron-capture $Q$ value for the $^{72}\mathrm{As}$ to $^{72}\mathrm{Ge}$ decay by measuring their atomic mass difference utilizing the double Penning trap mass spectrometer, JYFLTRAP. The $Q$ value was measured to be 4343.596(75) keV, which is more than a fiftyfold improvement in precision compared to the value in the most recent Atomic Mass Evaluation 2020. Furthermore, the new $Q$ value was found to be 12.4(40) keV (3.1 $\ensuremath{\sigma}$) lower. With the significant reduction of the uncertainty of the ground-state to ground-state $Q$ value combined with the level scheme of $^{72}\mathrm{Ge}$ from $\ensuremath{\gamma}$-ray spectroscopy, we confirm that the five potential ultralow $Q$-value ${\ensuremath{\beta}}^{+}$ decay or electron capture transitions are energetically forbidden, thus precluding all the transitions as possible candidates for the electron neutrino mass determination. However, the discovery of small negative $Q$ values opens up the possibility to use $^{72}\mathrm{As}$ for the study of virtual $\ensuremath{\beta}\text{\ensuremath{-}}\ensuremath{\gamma}$ transitions.

Mass measurements of the $^{69}$As, $^{70,71}$Se and $^{71}$Br isotopes, produced via fragmentation of a $^{124}$Xe primary beam at the FRS at GSI, have been performed with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS Ion Catcher with an unprecedented mass resolving power of almost 1,000,000. For the $^{69}$As isotope, this is the first direct mass measurement. A mass uncertainty of 22 keV was achieved with only 10 events. For the $^{70}$Se isotope, a mass uncertainty of 2.6 keV was obtained, corresponding to a relative accuracy of $\delta$m/m = 4.0$\times 10^{-8}$, with less than 500 events. The masses of the $^{71}$Se and $^{71}$Br isotopes were measured with an uncertainty of 23 and 16 keV, respectively. Our results for the $^{70,71}$Se and $^{71}$Br isotopes agree with the 2016 Atomic Mass Evaluation, and our result for the $^{69}$As isotope resolves the discrepancy between previous indirect measurements. We measured also the mass of $^{14}$N$^{15}$N$^{40}$Ar (A=69) with a relative accuracy of $\delta$m/m = 1.7$\times 10^{-8}$, the highest yet achieved with a MR-TOF-MS. Our results show that the measured restrengthening of the proton-neutron interaction ($\delta$V$_{pn}$) for odd-odd nuclei at the N=Z line above Z=29 (recently extended to Z=37) is hardly evident at N-Z=2, and not evident at N-Z=4. Nevertheless, detailed structure of $\delta$V$_{pn}$ along the N-Z=2 and N-Z=4 lines, confirmed by our mass measurements, may provide a hint regarding the ongoing $\approx$500 keV discrepancy in the mass value of the $^{70}$Br isotope, which prevents including it in the world average of ${Ft}$-value for superallowed 0$^+\rightarrow$ 0$^+$ $\beta$ decays. The reported work sets the stage for mass measurements with the FRS Ion Catcher of nuclei at and beyond the N=Z line in the same region of the nuclear chart, including the $^{70}$Br isotope., Comment: 11 pages, 4 figures, accepted for publication at Physical Review C

Accurate mass measurements of neutron-rich iron and cobalt isotopes $^{67}\mathrm{Fe}$ and $^{69,70}\mathrm{Co}$ have been realized with the JYFLTRAP double Penning-trap mass spectrometer. With novel ion-manipulation techniques, the masses of the $^{69,70}\mathrm{Co}$ ground states and the $1/{2}^{\ensuremath{-}}$ isomer in $^{69}\mathrm{Co}$ have been extracted for the first time. The measurements remove ambiguities in the previous mass values and yield a smoother trend on the mass surface, extending it beyond $N=40$. The moderate $N=40$ subshell gap has been found to weaken below $^{68}\mathrm{Ni}$, a region known for shape coexistence and increased collectivity. The excitation energy for the $1/{2}^{\ensuremath{-}}$ intruder state in $^{69}\mathrm{Co}$ has been determined for the first time and is compared to large-scale shell-model calculations. The new mass values also reduce significantly mass-related uncertainties for the astrophysical rapid neutron-capture process calculations.

The JYFLTRAP double Penning trap at the Ion Guide Isotope Separator On-Line (IGISOL) facility has been used to measure the atomic masses of 13 neutron-rich rare-earth isotopes. Eight of the nuclides, $^{161}$Pm, $^{163}$Sm, $^{164,165}$Eu, $^{167}$Gd, and $^{165,167,168}$Tb, were measured for the first time. The systematics of the mass surface has been studied via one- and two-neutron separation energies as well as neutron pairing-gap and shell-gap energies. The proton-neutron pairing strength has also been investigated. The impact of the new mass values on the astrophysical rapid neutron capture process has been studied. The calculated abundance distribution results in a better agreement with the solar abundance pattern near the top of the rare-earth abundance peak at around $A\approx165$., Comment: 15 pages, 17 figures

We report the first detection of the second-forbidden, nonunique, 2+→0+, ground-state transition in the β decay of F20. A low-energy, mass-separated F+20 beam produced at the IGISOL facility in Jyvaskyla, Finland, was implanted in a thin carbon foil and the β spectrum measured using a magnetic transporter and a plastic-scintillator detector. The β-decay branching ratio inferred from the measurement is bβ=[0.41±0.08(stat)±0.07(sys)]×10-5 corresponding to logft=10.89(11), making this one of the strongest second-forbidden, nonunique β transitions ever measured. The experimental result is supported by shell-model calculations and has significant implications for the final evolution of stars that develop degenerate oxygen-neon cores. Using the new experimental data, we argue that the astrophysical electron-capture rate on Ne20 is now known to within better than 25% at the relevant temperatures and densities. (Less)

A significant fraction of stars between 7 and 11 solar masses are thought to become supernovae, but the explosion mechanism is unclear. The answer depends critically on the rate of electron capture on ^{20}Ne in the degenerate oxygen-neon stellar core. However, because of the unknown strength of the transition between the ground states of ^{20}Ne and ^{20}F, it has not previously been possible to fully constrain the rate. By measuring the transition, we establish that its strength is exceptionally large and that it enhances the capture rate by several orders of magnitude. This has a decisive impact on the evolution of the core, increasing the likelihood that the star is (partially) disrupted by a thermonuclear explosion rather than collapsing to form a neutron star. Importantly, our measurement resolves the last remaining nuclear physics uncertainty in the final evolution of degenerate oxygen-neon stellar cores, allowing future studies to address the critical role of convection, which at present is poorly understood.

The decays of the β-delayed neutron emitters I137 and Rb95 have been studied with the total absorption γ-ray spectroscopy technique. The purity of the beams provided by the JYFLTRAP Penning trap at the ion guide isotope separator on-line facility in Jyvaskyla allowed us to carry out a campaign of isotopically pure measurements with the decay total absorption γ-ray spectrometer, a segmented detector composed of 18 NaI(Tl) modules. The contamination coming from the interaction of neutrons with the spectrometer has been carefully studied, and we have tested the use of time differences between prompt γ rays and delayed neutron interactions to eliminate this source of contamination. Due to the sensitivity of our spectrometer, we have found a significant amount of β intensity to states above the neutron separation energy that deexcite by γ rays, comparable to the neutron emission probability. The competition between γ deexcitation and neutron emission has been compared with Hauser-Feshbach calculations, and it can be understood as a nuclear structure effect. In addition, we have studied the impact of the β-intensity distributions determined in this work on reactor decay heat and reactor antineutrino spectrum summation calculations. The robustness of our results is demonstrated by a thorough study of uncertainties and with the reproduction of the spectra of the individual modules and the module-multiplicity gated spectra. This work represents the state-of-the-art of our analysis methodology for segmented total absorption spectrometers.

Monoisotopic samples of $^{107}\mathrm{Nb}$ nuclei, produced in the proton-induced fission of $^{238}\mathrm{U}$ and separated using the IGISOL mass separator coupled to a Penning trap, were used to perform $\ensuremath{\beta}$- and $\ensuremath{\gamma}$-coincidence spectroscopy of $^{107}\mathrm{Mo}$. Gamma transitions and excited levels in $^{107}\mathrm{Mo}$ were observed in $\ensuremath{\beta}$ decay for the first time. Spin and parity $1/{2}^{+}$ for the ground state of $^{107}\mathrm{Mo}$ is proposed, to replace the previous $5/{2}^{+}$ assignment. The experimental $\ensuremath{\beta}$-decay half-life of $^{107}\mathrm{Nb}$ was estimated to be $0.27\ifmmode\pm\else\textpm\fi{}0.02$ s.

A dedicated spectroscopic study of the β decay of 127Cd was conducted at the IGISOL facility at the University of Jyvaskyla. Following high-resolution mass separation in a Penning trap, β-γ-γ coincidences were used to considerably extend the decay scheme of 127In. The β-decaying 3/2+ and 11/2- states in 127Cd have been identified with the 127Cd ground state and the 283-keV isomer. Their respective half-lives have been measured to 0.45(+12-8)s and 0.36(4) s. The experimentally observed β feeding to excited states of 127In and the decay scheme of 127In are discussed in conjunction with large-scale shell-model calculations.

Even mass neutron-rich niobium isotopes are among the principal contributors to the reactor antineutrino energy spectrum. They are also among the most challenging to measure due to the refractory nature of niobium, and because they exhibit isomeric states lying very close in energy. The beta-intensity distributions of Nb-100gs,Nb-100m and Nb-102gs,Nb-02m beta decays have been determined using the total absorption.-ray spectroscopy technique. The measurements were performed at the upgraded Ion Guide Isotope Separator On-Line facility at the University of Jyvaskyla. Here, the double Penning trap system JYFLTRAP was employed to disentangle the beta decay of the isomeric states. The new data obtained in this challenging measurement have a large impact in antineutrino summation calculations. For the first time the discrepancy between the summation model and the reactor antineutrino measurements in the region of the shape distortion has been reduced.

Background: $\beta$-delayed multiple neutron emission has been observed for some nuclei with A$\leq$100, with $^{100}$Rb being the heaviest $\beta$2n emitter measured to date. So far, only 25 P$_{2n}$ values have been determined for the $\sim$300 nuclei that may decay in this way. Accordingly, it is of interest to measure P$_{2n}$ values for the other possible multiple neutron emitters throughout the chart of the nuclides. It is of particular interest to make such 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 astrophysical nucleosynthesis processes such as the $r$-process, and safety inputs for nuclear reactors. Purpose: To determine for the first time the two neutron branching ratio, P$_{2n}$ value, for $^{136}$Sb through a direct neutron measurement, and to provide precise P$_{1n}$ values for $^{136}$Sb and $^{136}$Te. Method: Pure beams were provided by the JYFLTRAP at the IGISOL facility of the University of Jyv\"askyl\"a, Finland. The purified ions were implanted into a moving tape at the end of the beam line. The detection setup consisted of a plastic scintillator placed right behind the implantation point, and the BELEN detector, based on neutron counters embedded in a polyethylene matrix. The analysis was based on the study of the $\beta$- and neutron- growth-and-decay curves and the $\beta$-one-neutron and $\beta$-two-neutron time correlations. Results: The P$_{2n}$ value of $^{136}$Sb was found to be 0.31(5)\% and the measured P$_{1n}$ values for $^{136}$Sb and $^{136}$Te were found to be 31.9(15)\% and 1.47(6)\%, respectively. The measured P$_{2n}$ value is a factor 20 smaller than predicted by the FRDM+QRPA model used for $r$-process calculations.

Monoisotopic samples of exotic, neutron-rich $^{117}\mathrm{Rh}$ nuclei, produced in the proton-induced fission of $^{238}\mathrm{U}$ and separated using the IGISOL mass separator coupled to the JYFLTRAP Penning trap, were used to perform $\ensuremath{\beta}$ and $\ensuremath{\gamma}$ coincidence spectroscopy of $^{117}\mathrm{Pd}$. The spin parity of the ground state of $^{117}\mathrm{Pd}$ was determined to be $1/{2}^{+}$ and the 19.1 ms isomer at 203.2 keV was assigned a spin-parity $7/{2}^{\ensuremath{-}}$. The $^{117}\mathrm{Rh}$ ${\ensuremath{\beta}}^{\ensuremath{-}}$-decay scheme was considerably extended, and various sequences of the levels were interpreted as resulting from the prolate, oblate, and triaxial nuclear shapes. Some of the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decays were considered as the allowed Gamow-Teller transitions. The experimental distribution of Gamow-Teller strength is discussed.

The beta decay of Tc-100 has been studied by using the total absorption gamma-ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility in Jyvaskyla. In this work the new Decay Total Absorption gamma-ray Spectrometer in coincidence with a cylindrical plastic beta detector has been employed. The beta intensity to the ground state obtained from the analysis is in good agreement with previous high-resolution measurements. However, differences in the feeding to the first-excited state as well as weak feeding to a new level at high excitation energy have been deduced from this experiment. Theoretical calculations performed in the quasiparticle random-phase approximation framework are also reported. Comparison of these calculations with our measurement serves as a benchmark for calculations of the double beta decay of Mo-100.

Excited levels of $^{88}\mathrm{Br}$ populated in the $\ensuremath{\beta}$ decay of $^{88}\mathrm{Se}$ have been studied by means of $\ensuremath{\beta}\ensuremath{\gamma}$ and $\ensuremath{\gamma}\ensuremath{\gamma}$ spectroscopy methods. Neutron-rich parent $^{88}\mathrm{Se}$ nuclei were produced with proton-induced fission of $^{238}\mathrm{U}$ using the Ion Guide Isotope Separator On-Line (IGISOL) method and separated from contaminants using a dipole magnet and the coupled JYFLTRAP Penning trap at the Accelerator Laboratory of the University of Jyv\"askyl\"a. The level scheme of $^{88}\mathrm{Br}$ has been constructed and $logft$ values of levels were determined. The ground-state spin of $^{88}\mathrm{Br}$ is now firmly determined to be ${1}^{\ensuremath{-}}$. Low-energy levels in $^{88}\mathrm{Br}$ were interpreted as members of the $\ensuremath{\pi}{p}_{3/2}{(\ensuremath{\nu}{d}_{5/2})}^{3}, \ensuremath{\pi}{p}_{3/2}^{\ensuremath{-}1}{(\ensuremath{\nu}{d}_{5/2})}^{3}, \ensuremath{\pi}{f}_{5/2}^{\ensuremath{-}1}{(\ensuremath{\nu}{d}_{5/2})}^{3}$, and $\ensuremath{\pi}{g}_{9/2}\ensuremath{\nu}{g}_{7/2}$ multiplets. The shell-model calculations performed in this work reproduce well the experimental results.

Precise measurements of superallowed ${0}^{+}\ensuremath{\rightarrow}{0}^{+}$ $\ensuremath{\beta}$ decay presently provide the most precise value for the weak mixing amplitude ${V}_{u\phantom{\rule{0}{0ex}}d}$. As the largest element of the CKM matrix, ${V}_{u\phantom{\rule{0}{0ex}}d}$ is a critical piece of the Standard Model of the electroweak interaction. The new, precise Penning-trap mass measurement of the decay energy for the superallowed transition in ${}^{42}$Sc opens the door for a much more precise $f\phantom{\rule{0}{0ex}}t$ value determination if its half-life can be measured more precisely as well.

The mass of $^{31}\mathrm{Cl}$ has been measured with the JYFLTRAP double-Penning-trap mass spectrometer at the Ion Guide Isotope Separator On-Line (IGISOL) facility. The determined mass-excess value, $\ensuremath{-}7034.7(34)$ keV, is 15 times more precise than in the Atomic Mass Evaluation 2012. The quadratic form of the isobaric multiplet mass equation for the $T=3/2$ quartet at $A=31$ fails $({\ensuremath{\chi}}_{n}^{2}=11.6)$ and a nonzero cubic term, $d=\ensuremath{-}3.5(11)$ keV, is obtained when the new mass value is adopted. $^{31}\mathrm{Cl}$ has been found to be less proton-bound, with a proton separation energy of ${S}_{p}=264.6(34)$ keV. Energies for the excited states in $^{31}\mathrm{Cl}$ and the photodisintegration rate on $^{31}\mathrm{Cl}$ have been determined with significantly improved precision by using the new ${S}_{p}$ value. The improved photodisintegration rate helps to constrain astrophysical conditions where $^{30}\mathrm{S}$ can act as a waiting point in the rapid proton capture process in type-I x-ray bursts.

The atomic mass relations among the mass triplet ^{96}Zr, ^{96}Nb, and ^{96}Mo have been determined by means of high-precision mass measurements using the JYFLTRAP mass spectrometer at the IGISOL facility of the University of Jyvaskyla. We report Q values for the ^{96}Zr single and double β decays to ^{96}Nb and ^{96}Mo, as well as the Q value for the ^{96}Nb single β decay to ^{96}Mo, which are Q_{β}(^{96}Zr)=163.96(13), Q_{ββ}(^{96}Zr)=3356.097(86), and Q_{β}(^{96}Nb)=3192.05(16) keV. Of special importance is the ^{96}Zr single β-decay Q value, which has never been determined directly. The single β decay, whose main branch is fourfold unique forbidden, is an alternative decay path to the ^{96}Zr ββ decay, and its observation can provide one of the most direct tests of the neutrinoless ββ-decay nuclear-matrix-element calculations, as these can be simultaneously performed for both decay paths with no further assumptions. The theoretical single β-decay rate has been re-evaluated using a shell-model approach, which indicates a ^{96}Zr single β-decay lifetime within reach of an experimental verification. The uniqueness of the decay also makes such an experiment interesting for an investigation into the origin of the quenching of the axial-vector coupling constant g_{A}.

The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. (92)Rb makes the dominant contribution to the reactor antineutrino spectrum in the 5-8 MeV range but its decay properties are in question. We have studied (92)Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed.

The $\ensuremath{\beta}$-feeding probabilities for three important contributors to the decay heat in nuclear reactors, namely ${}^{102,104,105}$Tc, have been measured using the total absorption spectroscopy technique. For the measurements, sources of very high isobaric purity have been obtained using a Penning trap (JYFLTRAP). A detailed description of the data analysis is given and the results are compared with high-resolution measurements and theoretical calculations.

The double Penning trap mass spectrometer JYFLTRAP has been employed to measure masses and excitation energies for $11/2^-$ isomers in $^{121}$Cd, $^{123}$Cd, $^{125}$Cd and $^{133}$Te, for $1/2^-$ isomers in $^{129}$In and $^{131}$In, and for $7^-$ isomers in $^{130}$Sn and $^{134}$Sb. These first direct mass measurements of the Cd and In isomers reveal deviations to the excitation energies based on results from beta-decay experiments and yield new information on neutron- and proton-hole states close to $^{132}$Sn. A new excitation energy of 144(4) keV has been determined for $^{123}$Cd$^m$. A good agreement with the precisely known excitation energies of $^{121}$Cd$^m$, $^{130}$Sn$^m$, and $^{134}$Sb$^m$ has been found.

The excited levels of ${}^{115}$Ag have been studied via the beta decay of ${}^{115}$Pd and ${}^{115}$Pd${}^{m}$. The beta-decay schemes for both states have been considerably extended, especially the scheme following the decay of ${}^{115}$Pd${}^{m}$ which was practically unknown before this work. Transition intensities and ${\mathrm{log}}_{10}ft$ values are reported, which have been missing in the literature. A set of levels around 2 MeV has been found to be strongly populated by the beta decay of the ground state of ${}^{115}$Pd and is suggested to have a three-quasiparticle nature. The properties of excited levels have been compared with the level systematics of lighter neutron-rich silver isotopes, and new spin assignments as well as identification of Nilsson states in ${}^{115}$Ag have been made.

Atomic masses of the neutron-rich isotopes $^{121--128}\mathrm{Cd}$, $^{129,131}\mathrm{In}$, $^{130--135}\mathrm{Sn}$, $^{131--136}\mathrm{Sb}$, and $^{132--140}\mathrm{Te}$ have been measured with high precision (10 ppb) using the Penning-trap mass spectrometer JYFLTRAP. Among these, the masses of four $r$-process nuclei $^{135}\mathrm{Sn}$, $^{136}\mathrm{Sb}$, and $^{139,140}\mathrm{Te}$ were measured for the first time. An empirical neutron pairing gap expressed as the odd-even staggering of isotopic masses shows a strong quenching across $N=82$ for Sn, with a $Z$ dependence that is unexplainable by the current theoretical models.

Accurate measurements of the B-8 neutrino spectrum are important for the interpretation of solar neutrino data. Experimentally, the B-8 neutrino spectrum can be obtained from the measurement of the beta-delayed alpha spectrum. We report on an alpha-alpha coincidence measurement performed at the IGISOL facility in Jyvaskyla, Finland. Our measurement allows extensive cross-checks to be performed and gives a more intense neutrino spectrum at high energies compared to the present standard. The deviation reaches 4% at the end point of the spectrum. Below 11 MeV, the deviation is less than 1%.

The ${Q}_{\mathrm{EC}}$ values of the superallowed ${\ensuremath{\beta}}^{+}$ emitters $^{10}\mathrm{C}$, $^{34}\mathrm{Ar}$, $^{38}\mathrm{Ca}$, and $^{46}\mathrm{V}$ have been measured with the JYFLTRAP Penning-trap mass spectrometer to be 3648.12(8), 6061.83(8), 6612.12(7), and 7052.44(10) keV, respectively. All four values are substantially improved in precision over previous results. Of the well-known superallowed emitters, only $^{14}\mathrm{O}$ has yet to have had its ${Q}_{\mathrm{EC}}$ value measured with a Penning trap.

Exotic, neutron-rich nuclei of mass $A=115$ produced in proton-induced fission of $^{238}\mathrm{U}$ were extracted using the IGISOL mass separator. The beam of isobars was transferred to the JYFLTRAP Penning trap system for further separation to the isotopic level. Monoisotopic samples of $^{115}\mathrm{Ru}$ nuclei were used for $\ensuremath{\gamma}$and $\ensuremath{\beta}$ coincidence spectroscopy. In $^{115}\mathrm{Ru}$ we have observed excited levels, including an isomer with a half-life of 76(6) ms and ($7/{2}^{\ensuremath{-}}$) spin and parity. The first excited 61.7-keV level in $^{115}\mathrm{Ru}$ with spins and parity ($3/{2}^{+}$) may correspond to an $\mathit{oblate}$ $3/{2}^{+}$[431] Nilsson orbital. A half-life of 318(19) ms for the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of the ($1/{2}^{+}$) ground state in $^{115}\mathrm{Ru}$ has been firmly established in two independent measurements, a value which is significantly shorter than that previously reported.

The {beta} feeding probability of {sup 102,104,105,106,107}Tc, {sup 105}Mo, and {sup 101}Nb nuclei, which are important contributors to the decay heat in nuclear reactors, has been measured using the total absorption technique. We have coupled for the first time a total absorption spectrometer to a Penning trap in order to obtain sources of very high isobaric purity. Our results solve a significant part of a long-standing discrepancy in the {gamma} component of the decay heat for {sup 239}Pu in the 4-3000 s range.

Masses of $^{56,57}\mathrm{Fe}$, $^{53}\mathrm{Co}$${}^{m}$, $^{53,56}\mathrm{Co}$, $^{55,56,57}\mathrm{Ni}$, $^{57,58}\mathrm{Cu}$, and $^{59,60}\mathrm{Zn}$ have been determined with the JYFLTRAP Penning trap mass spectrometer at the Ion-Guide Isotope Separator On-Line facility with a precision of $\ensuremath{\delta}m/m\ensuremath{\leqslant}3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$. The ${Q}_{\mathrm{EC}}$ values for $^{53}\mathrm{Co}$, $^{55}\mathrm{Ni}$, $^{56}\mathrm{Ni}$, $^{57}\mathrm{Cu}$, $^{58}\mathrm{Cu}$, and $^{59}\mathrm{Zn}$ have been measured directly with a typical precision of better than $0.7 \mathrm{keV}$ and Coulomb displacement energies have been determined. The $Q$ values for proton captures on $^{55}\mathrm{Co}$, $^{56}\mathrm{Ni}$, $^{58}\mathrm{Cu}$, and $^{59}\mathrm{Cu}$ have been measured directly. The precision of the proton-capture $Q$ value for $^{56}\mathrm{Ni}$$(p,\ensuremath{\gamma})$$^{57}\mathrm{Cu}$, ${Q}_{(p,\ensuremath{\gamma})}=689.69(51) \mathrm{keV}$, crucial for astrophysical $\mathit{rp}$-process calculations, has been improved by a factor of 37. The excitation energy of the proton-emitting spin-gap isomer $^{53}\mathrm{Co}$${}^{m}$ has been measured precisely, ${E}_{x}=3 174.3(10) \mathrm{keV}$, and a Coulomb energy difference of $133.9(10) \mathrm{keV}$ for the $19/{2}^{\ensuremath{-}}$ state has been obtained. Except for $^{53}\mathrm{Co}$, the mass values have been adjusted within a network of 17 frequency ratio measurements between 13 nuclides, which allowed also a determination of the reference masses $^{55}\mathrm{Co}$, $^{58}\mathrm{Ni}$, and $^{59}\mathrm{Cu}$.

Excited states in $^{115}\mathrm{Pd}$, populated following the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{115}\mathrm{Rh}$ have been studied by means of $\ensuremath{\gamma}$ spectroscopy after the Penning-trap station at the IGISOL facility, University of Jyv\"askyl\"a. The $1$$/$$2$${}^{+}$ spin and parity assignment of the ground state of $^{115}\mathrm{Pd}$, confirmed in this work, may indicate a transition to an oblate shape in Pd isotopes at high neutron number.

The β decays of 12N and 12B have been studied at KVI and JYFL to resolve the composition of the broad and interfering 0+ and 2+ strengths in the triple-α continuum. For the first time a complete treatment of 3α decay is presented including all major breakup channels. A multilevel, many-channel R-matrix formalism has been developed for the complete description of the breakup in combination with the recently published separate analysis of angular correlations. We find that, in addition to the Hoyle state at 7.65 MeV, more than one 0+ and 2+ state is needed to reproduce the spectra. Broad 03+ and 22+ states are found between 10.5 and 12 MeV in this work. The presence of β strength up to the 12N Q-value window suggests the presence of additional 0+ and 2+ components in the 12C structure at energies above 12.7 MeV.

The mass excess of the proton-rich nucleus $^{23}\mathrm{Al}$ has been measured with the JYFLTRAP Penning trap setup. As a result of our experiment we obtain a mass excess of 6748.07(34) keV, and by combining the value to existing experimental data we have tested the validity of the isobaric multiplet mass equation $(\mathrm{IMME})$ for the $T=3/2$ quartet in the $A=23$ isobar. The fit to the IMME results in a vanishing cubic term equivalent to zero with high precision [$0.22(42)$ keV].

Absolute branching ratios to unbound states in C-12 populated in the beta decays of N-12 and B-12 are reported. Clean sources of N-12 and B-12 were obtained using the isotope separation on-line (ISOL) method. The relative branching ratios to the different populated states were extracted using single-alpha as well as complete kinematics triple-alpha spectra. These two largely independent methods give consistent results. Absolute normalization is achieved via the precisely known absolute branching ratio to the bound 4.44 MeV state in C-12. The extracted branching ratios to the unbound states are a factor of three more precise than previous measurements. Branching ratios in the decay of Na-20 are also extracted and used to check the results.

The triple-alpha-particle breakup of states in the triple-alpha continuum of C-12 has been investigated by way of coincident detection of all three alpha particles of the breakup. The states have been fed in the beta decay of N-12 and B-12, and the alpha particles measured using a setup that covers all of the triple-alpha phase space. Contributions from the breakup through the Be-8(0(+)) ground state as well as other channels-interpreted as breakup through excited energies in Be-8-have been identified. Spins and parities of C-12 triple-alpha continuum states are deduced from the measured phase-space distributions for breakup through Be-8 above the ground state by comparison to a fully symmetrized sequential R-matrix description of the breakup. At around 10 MeV in C-12, the breakup is found to be dominated by 0(+) strength breaking up through the ghost of the Be-8(0(+)) ground state with L = 0 angular momentum between the first emitted alpha particle and the intermediate Be-8 nucleus. For C-12 energies above the 12.7 MeV 1(+) state, however, L = 2 breakup of a C-12 2(+) state through the Be-8(2(+)) excited state dominates. Furthermore, the possibility of a 2(+) excited state in the 9-12 MeV region of C-12 is investigated.

The half-life, the branching ratio, and the decay $Q$ value of the superallowed $\ensuremath{\beta}$ emitter $^{42}\mathrm{Ti}$ were measured in an experiment performed at the JYFLTRAP facility of the Accelerator Laboratory of the University of Jyv\"askyl\"a. $^{42}\mathrm{Ti}$ is the heaviest ${T}_{z}=\ensuremath{-}1$ nucleus for which high-precision measurements of these quantities have been tried. The half-life (${T}_{1/2}=208.14\ifmmode\pm\else\textpm\fi{}0.45$ ms) and the $Q$ value [${Q}_{\mathrm{EC}}=7016.83(25)$ keV] are close to or reach the required precision of about 0.1%. The branching ratio for the superallowed decay branch [$\mathrm{BR}=47.7(12)%$], a by-product of the half-life measurement, does not reach the necessary precision yet. Nonetheless, these results allow one to determine the experimental $\mathit{ft}$ value and the corrected $\mathcal{F}t$ value to be 3114(79) and 3122(79) s, respectively.

The $Q$ value of the $^{112}\mathrm{Sn}$ double-beta decay was determined by using a Penning trap mass spectrometer. The new atomic-mass difference between $^{112}\mathrm{Sn}$ and $^{112}\mathrm{Cd}$ of 1919.82(16) keV is 25 times more precise than the previous value of 1919(4) keV. This result removes the possibility of enhanced resonance capture of the neutrinoless double-EC decay to the excited ${0}^{+}$ state at 1871.00(19) keV in $^{112}\mathrm{Cd}$.

The nuclides 104-108Sn, 106-110Sb, 108,109Te, and 111I at the expected endpoint of the astrophysical rp process have been produced in 58Ni+natNi fusion-evaporation reactions at IGISOL and their mass values were precisely measured with the JYFLTRAP Penning trap mass spectrometer. For 106Sb, 108Sb, and 110Sb these are the first direct experimental mass results obtained. The related one-proton separation energies have been derived and the value for 106Sb, Sp=424(8) keV, shows that the branching into the closed SnSbTe cycle in the astrophysical rp process is weaker than expected.

The ${Q}_{\mathrm{EC}}$ value of the superallowed $\ensuremath{\beta}$ emitter $^{26}\mathrm{Si}$ has been measured with the JYFLTRAP Penning trap facility to be 4840.85(10) keV which is ten times more precise than any previous measurement. This leaves only the branching ratio to be improved before the $\mathcal{F}t$ value of $^{26}\mathrm{Si}$ can be used to test the conserved vector current hypothesis. As a consequence, the $^{25}\mathrm{Al}(p,\ensuremath{\gamma})^{26}\mathrm{Si}$ reaction $Q$-value (${Q}_{p\ensuremath{\gamma}}$) was improved to be 5513.7(5) keV, limited now by the mass excess of $^{25}\mathrm{Al}$. The new ${Q}_{p\ensuremath{\gamma}}$ value changes the stellar production rate of $^{26}\mathrm{Si}$ in nova ignition temperatures by about 10%.

We present a measurement of the electron-capture branch of $^{100}\mathrm{Tc}$. Our value, $B(\mathrm{EC})=(2.6\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, implies that the $^{100}\mathrm{Mo}$ neutrino absorption cross section to the ground state of $^{100}\mathrm{Tc}$ is roughly 50% larger than previously thought. Disagreement between the experimental value and QRPA calculations relevant to double-$\ensuremath{\beta}$ decay matrix elements persists. We find agreement with previous measurements of the 539.5- and 590.8-keV $\ensuremath{\gamma}$-ray intensities.

The masses of very neutron-deficient nuclides close to the astrophysical r p- and {nu} p-process paths have been determined with the Penning trap facilities JYFLTRAP at JYFL/Jyvaeskylae and SHIPTRAP at GSI/Darmstadt. Isotopes from yttrium (Z=39) to palladium (Z=46) have been produced in heavy-ion fusion-evaporation reactions. In total, 21 nuclides were studied, and almost half of the mass values were experimentally determined for the first time: {sup 88}Tc, {sup 90-92}Ru, {sup 92-94}Rh, and {sup 94,95}Pd. For the {sup 95}Pd{sup m}, (21/2{sup +}) high-spin state, a first direct mass determination was performed. Relative mass uncertainties of typically {delta}m/m=5x10{sup -8} were obtained. The impact of the new mass values has been studied in {nu} p-process nucleosynthesis calculations. The resulting reaction flow and the final abundances are compared with those obtained with the data of the Atomic Mass Evaluation 2003.

Nuclides in the vicinity of {sup 94}Ag have been studied with the Penning trap mass spectrometer JYFLTRAP at the Ion-Guide Isotope Separator On-Line. The masses of the two-proton-decay daughter {sup 92}Rh and the beta-decay daughter {sup 94}Pd of the high-spin isomer in {sup 94}Ag have been measured, and the masses of {sup 93}Pd and {sup 94}Ag have been deduced. When combined with the data from the one-proton- or two-proton-decay experiments, the results lead to contradictory mass excess values for the high-spin isomer in {sup 94}Ag, -46 370(170) or -44 970(100) keV, corresponding to excitation energies of 6960(400) or 8360(370) keV, respectively.

Atomic masses of the neutron-rich isotopes $^{76--80}\mathrm{Zn}$, $^{78--83}\mathrm{Ga}$, $^{80--85}\mathrm{Ge}$, $^{81--87}\mathrm{As}$, and $^{84--89}\mathrm{Se}$ have been measured with high precision using the Penning trap mass spectrometer JYFLTRAP at the IGISOL facility. The masses of $^{82,83}\mathrm{Ga}$, $^{83--85}\mathrm{Ge}$, $^{84--87}\mathrm{As}$, and $^{89}\mathrm{Se}$ were measured for the first time. These new data represent a major improvement in the knowledge of the masses in this neutron-rich region. Two-neutron separation energies provide evidence for the reduction of the $N=50$ shell gap energy towards germanium ($Z=32$) and a subsequent increase at gallium ($Z=31$). The data are compared with a number of theoretical models. An indication of the persistent rigidity of the shell gap towards nickel ($Z=28$) is obtained.