Direct determination of the atomic mass difference of the pairs As 76 − Se 76 and Tb 155 − Gd 155 rules out As 76 and Tb 155 as possible candidates for electron (anti)neutrino mass measurements

Measurement of the $2^+\rightarrow 0^+$ ground-state transition in the $\beta$ decay of $^{20}$F

We report the first detection of the second-forbidden, non-unique, $2^+\rightarrow 0^+$, ground-state transition in the $\beta$ decay of $^{20}$F. A low-energy, mass-separated $^{20}\rm{F}^+$ beam produced at the IGISOL facility in Jyv\"askyl\"a, Finland, was implanted in a thin carbon foil and the $\beta$ spectrum measured using a magnetic transporter and a plastic-scintillator detector. The $\beta$-decay branching ratio inferred from the measurement is $b_{\beta} = [ 0.41\pm 0.08\textrm{(stat)}\pm 0.07\textrm{(sys)}] \times 10^{-5}$ corresponding to $\log ft = 10.89(11)$, making this one of the strongest second-forbidden, non-unique $\beta$ transitions ever measured. The experimental resu…

Direct measurement of the mass difference of $^{72}$As-$^{72}$Ge rules out $^{72}$As as a promising $\beta$-decay candidate to determine the neutrino mass

We report the first direct determination of the ground-state to ground-state electron-capture $Q$-value for the $^{72}$As to $^{72}$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 50-fold 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 $\sigma$) lower. With the significant reduction of the uncertainty of the ground-state to ground-state $Q$-value value combined with the level scheme of $^{72}$Ge from $\gamma$-ray spectroscopy, we confirm that th…

High-precision electron-capture Q value measurement of 111In for electron-neutrino mass determination

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 deca…

High-Precision Q -Value Measurement Confirms the Potential of Cs 135 for Absolute Antineutrino Mass Scale Determination

High-precision measurement of a low Q value for allowed β−-decay of 131I related to neutrino mass determination

The ground-state-to-ground-state β−-decay 131I (7/2+) → 131Xe (3/2+) Q value was determined with high precision utilizing the double Penning trap mass spectrometer JYFLTRAP at the IGISOL facility. The Q value of this β−-decay was found to be Q = 972.25(19) keV through a cyclotron frequency ratio measurement with a relative precision of 1.6 × 10−9. This was realized using the phase-imaging ion-cyclotron-resonance technique. The new Q value is more than 3 times more precise and 2.3σ higher (1.45 keV) than the value extracted from the Atomic Mass Evaluation 2020. Our measurement confirms that the β−-decay to the 9/2+ excited state at 971.22(13) keV in 131Xe is energetically allowed with a Q va…

Direct determination of the excitation energy of the quasistable isomer 180mTa

180mTa is a naturally abundant quasistable nuclide and the longest-lived nuclear isomer known to date. It is of interest, among others, for the search for dark matter, for the development of a γ laser, and for astrophysics. So far, its excitation energy has not been measured directly but has been based on an evaluation of available nuclear reaction data. We have determined the excitation energy of this isomer with high accuracy using the Penning-trap mass spectrometer JYFLTRAP. The determined mass difference between the ground and isomeric states of 180Ta yields an excitation energy of 76.79(55) keV for 180mTa. This is the first direct measurement of the excitation energy and provides a bet…

Experimental study of $^{100}$Tc $\beta$ decay with total absorption $\gamma$-ray spectroscopy

International audience; The β decay of Tc100 has been studied by using the total absorption γ-ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility in Jyväskylä. In this work the new Decay Total Absorption γ-ray Spectrometer in coincidence with a cylindrical plastic β detector has been employed. The β 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 approximatio…

Electron-capture branch of Tc-100 and tests of nuclear wave functions for double-beta decays

We present a measurement of the electron-capture branch of 100Tc. Our value, B(EC)=(2.6±0.4)×10−5, implies that the 100Mo neutrino absorption cross section to the ground state of 100Tc is roughly one third larger than previously thought. Compared to previous measurements, our value of B(EC) prevents a smaller disagreement with QRPA calculations relevant to double-β decay matrix elements.

Measurement of the 2+--0+ ground-state transition in the ß decay of 20F

12 pags., 16 figs., 4 tabs.

Total Absorption Spectroscopy Study of $^{92}$Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape

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 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.

Observation of an ultralow- Q -value electron-capture channel decaying to As75 via a high-precision mass measurement

Measurement of the 2+→0+ ground-state transition in the β decay of 20F

We report the first detection of the second-forbidden, nonunique, 2+→0+, ground-state transition in the β decay of 20F. A low-energy, mass-separated 20F+ beam produced at the IGISOL facility in Jyväskylä, 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 tha…

β - and γ -spectroscopy study of Pd119 and Ag119

VADER: A novel decay station for actinide spectroscopy

Nuclear instruments & methods in physics research / B 540, 148 - 150 (2023). doi:10.1016/j.nimb.2023.04.021

Observation of an ultralow-Q-value electron-capture channel decaying to 75As via a high-precision mass measurement

A precise determination of the atomic mass of 75As has been performed utilizing the double Penning trap mass spectrometer, JYFLTRAP. The mass excess is measured to be −73035.519(42)keV/c2, which is a factor of 21 more precise and 1.3(9)keV/c2 lower than the adopted value in the newest Atomic Mass Evaluation (AME2020). This value has been used to determine the ground-state–to–ground-state electron-capture decay Q value of 75Se and β− decay Q value of 75Ge, which are derived to be 866.041(81) keV and 1178.561(65) keV, respectively. Using the nuclear energy-level data of 860.00(40) keV, 865.40(50) keV (final states of electron capture), and 1172.00(60) keV (final state of β− decay) for the exc…

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

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…

Measurement of key resonance states for the P30(p,γ)S31 reaction rate, and the production of intermediate-mass elements in nova explosions

We report the first experimental constraints on spectroscopic factors and strengths of key resonances in the P30(p,γ)S31 reaction critical for determining the production of intermediate-mass elements up to Ca in nova ejecta. The P30(d,n)S31 reaction was studied in inverse kinematics using the GRETINA γ -ray array to measure the angle-integrated cross-sections of states above the proton threshold. In general, negative-parity states are found to be most strongly produced but the absolute values of spectroscopic factors are typically an order of magnitude lower than predicted by the shell-model calculations employing WBP Hamiltonian for the negative-parity states. The results clearly indicat…

Single-particle shell strengths near the doubly magic nucleus Ni and the Ni( , ) Cu reaction rate in explosive astrophysical burning

Angle-integrated cross-section measurements of the $^{56}$Ni(d,n) and (d,p) stripping reactions have been performed to determine the single-particle strengths of low-lying excited states in the mirror nuclei pair $^{57}$Cu−$^{57}$Ni situated adjacent to the doubly magic nucleus $^{56}$Ni. The reactions were studied in inverse kinematics utilizing a beam of radioactive $^{56}$Ni ions in conjunction with the GRETINA γ-array. Spectroscopic factors are compared with new shell-model calculations using a full pf model space with the GPFX1A Hamiltonian for the isospin-conserving strong interaction plus Coulomb and charge-dependent Hamiltonians. These results were used to set new constraints on the…

Determination of β-decay ground state feeding of nuclei of importance for reactor applications

In β-decay studies the determination of the decay probability to the ground state (g.s.) of the daughter nucleus often suffers from large systematic errors. The difficulty of the measurement is related to the absence of associated delayed γ-ray emission. In this work we revisit the 4πγ−β method proposed by Greenwood and collaborators in the 1990s, which has the potential to overcome some of the experimental difficulties. Our interest is driven by the need to determine accurately the β-intensity distributions of fission products that contribute significantly to the reactor decay heat and to the antineutrinos emitted by reactors. A number of such decays have large g.s. branches. The method is…

Precision mass measurements of $^{67}$Fe and $^{69,70}$Co : Nuclear structure toward N=40 and impact on r -process reaction rates

International audience; Accurate mass measurements of neutron-rich iron and cobalt isotopes Fe67 and Co69,70 have been realized with the JYFLTRAP double Penning-trap mass spectrometer. With novel ion-manipulation techniques, the masses of the Co69,70 ground states and the 1/2− isomer in Co69 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 Ni68, a region known for shape coexistence and increased collectivity. The excitation energy for the 1/2− intruder state in Co69 has been determined for the first tim…

Low-spin excitations in 89Br populated in β−decay of 89Se

Low-spin, excited states of the 89Br nucleus, populated in β− decay of 89Se have been studied for the first time. The 89Se nuclei were produced in proton-induced fission of natural thorium using the IGISOL facility and separated using a dipole magnet and the coupled JYFLTRAP Penning trap. Gamma radiation following the β− decay of 89Se was measured with an array of high-resolution germanium detectors. Levels scheme of 89Br was extended by 12 new levels and 31 new γ transitions. Spin-parity (3/2+) has been proposed for the ground state of the 89Se mother nucleus, replacing the (5/2+) assignment reported in data bases. The observed Gamow-Teller β− transition to the 1754.5-keV level indicates a…

Dy159 Electron-Capture: A New Candidate for Neutrino Mass Determination

International audience; The ground state to ground state electron-capture Q value of Dy159 (3/2-) has been measured directly using the double Penning trap mass spectrometer JYFLTRAP. A value of 364.73(19) keV was obtained from a measurement of the cyclotron frequency ratio of the decay parent Dy159 and the decay daughter Tb159 ions using the novel phase-imaging ion-cyclotron resonance technique. The Q values for allowed Gamow-Teller transition to 5/2- and the third-forbidden unique transition to 11/2+ state with excitation energies of 363.5449(14) keV and 362.050(40) keV in Tb159 were determined to be 1.18(19) keV and 2.68(19) keV, respectively. The high-precision Q value of transition 3/2-…

Applications of the total absorption technique to improve reactor decay heat calculations: study of the beta decay of [sup 102,104,105]Tc

The decay heat of the fission products plays an important role in predicting the heat‐up of nuclear fuel after reactor shutdown. This form of energy release is calculated as the sum of the energy‐weighted activities of all fission products P(t) = ΣEiλiNi(t), where Ei is the decay energy of nuclide i (gamma and beta component), λi is the decay constant of nuclide i and Ni(t) is the number of nuclide i at cooling time t. Even though the reproduction of the measured decay heat has improved in recent years, there is still a long standing discrepancy at t∼1000 s cooling time for some fuels. A possible explanation for this disagreement can been found in the work of Yoshida et al. [1], who demonst…

Factors explaining being present at work in the forest industry, case–control study

Objectives: The aim of the study was to examine factors explaining few sickness absence hours (=SAH) among forest industry employees. Methods: The source population consisted of 636 forest industry employees in Finland, of which 140 were used as cases (SAH ≤ 1.5% during the past 6.5 years). Controls (140) were randomly selected from the source population (SAH > 1.5%). The study data were collected via a questionnaire. The response rate was 65.4% (mean age 48.5 years, men 67%). Discriminant and log-linear analysis were used to examine the relationships between variables and study groups. Results: Workers are more likely to have few sickness absences when their overall subjective health condi…

Direct measurement of the mass difference of 72As-72Ge rules out 72As as a promising β-decay candidate to determine the neutrino mass

Preprint of paper published on Physical Review C We report the first direct determination of the ground-state to ground-state electron-capture Q-value for the 72As to 72Ge 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 50-fold improvement in precision compared to the value in the most recent Atomic Mass Evaluation 2020. Furthermore, the new Qvalue was found to be 12.4(40) keV (3.1 σ) lower. With the significant reduction of the uncertainty of the ground-state to ground-state Q-value value combined with the level scheme of 72Ge from γ-ray spectro…

High-precision Q-value measurement and nuclear matrix element calculations for the double-β decay of 98Mo

The 98Mo double-beta decay Q-value has been measured, and the corresponding nuclear matrix elements of neutrinoless double-beta (0νββ) decay and the standard two-neutrino double-beta (2νββ) decay have been provided by nuclear theory. The double-beta decay Q-value has been determined as Qββ=113.668(68) keV using the JYFLTRAP Penning trap mass spectrometer. It is in agreement with the literature value, Qββ=109(6) keV, but almost 90 times more precise. Based on the measured Q-value, precise phase-space factors for 2νββ decay and 0νββ decay, needed in the half-life predictions, have been calculated. Furthermore, the involved nuclear matrix elements have been computed in the proton–neutron quasi…

Study of the Ti44(α,p)V47 reaction and implications for core collapse supernovae

The underlying physics triggering core collapse supernovae is not fully understood but observations of material ejected during such events helps to solve this puzzle. In particular, several satellite based γ -ray observations of the isotope 44 Ti have been reported recently. Conveniently, the amount of this isotope in stellar ejecta is thought to depend critically on the explosion mechanism. The most influential reaction to the amount of 44 Ti in supernovae is Ti44(α,p)V47 . Here we report on a direct study of this reaction conducted at the REX-ISOLDE facility, CERN. The experiment was performed with a 44 Ti beam at Elab=2.16 MeV/u , corresponding to an energy distribution, for reacting …

Study of the $��$-decay of $^{100}$Tc with Total Absorption $��$-Ray Spectroscopy

The \b{eta}-decay of 100 Tc has been studied using the Total Absorption ��-Ray Spectroscopy technique at IGISOL. In this work the new DTAS spectrometer in coincidence with a cylindrical plastic \b{eta} detector has been employed. The \b{eta}-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 (QRPA) framework are also reported. Comparison of these calculations with our measu…

Results of DTAS Campaign at IGISOL : Overview

The β decays of more than twenty fission fragments were measured in the first experiments with radioactive-ion beams employing the Decay Total Absorption γ-ray Spectrometer. In this work, we summarize the main results obtained so far from this experimental campaign carried out at the Ion Guide Isotope Separator On-Line facility. The advances introduced for these studies represent the state-of-the-art of our analysis methodology for segmented spectrometers. peerReviewed

New constraints on the Al25(p,γ) reaction and its influence on the flux of cosmic γ rays from classical nova explosions

The astrophysical 25Al(p,γ)26Si reaction represents one of the key remaining uncertainties in accurately modeling the abundance of radiogenic 26Al ejected from classical novae. Specifically, the strengths of key proton-unbound resonances in 26Si, that govern the rate of the 25Al(p,γ) reaction under explosive astrophysical conditions, remain unsettled. Here, we present a detailed spectroscopy study of the 26Si mirror nucleus 26Mg. We have measured the lifetime of the 3+, 6.125-MeV state in 26Mg to be 19(3)fs and provide compelling evidence for the existence of a 1− state in the T=1,A=26 system, indicating a previously unaccounted for ℓ=1 resonance in the 25Al(p,γ) reaction. Using the present…

Precision mass measurements of Fe 67 and Co 69 , 70 : Nuclear structure toward N = 40 and impact on r -process reaction rates

Study of the $\beta$-decay of $^{100}$Tc with Total Absorption $\gamma$-Ray Spectroscopy

The \b{eta}-decay of 100 Tc has been studied using the Total Absorption {\gamma}-Ray Spectroscopy technique at IGISOL. In this work the new DTAS spectrometer in coincidence with a cylindrical plastic \b{eta} detector has been employed. The \b{eta}-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 (QRPA) framework are also reported. Comparison of these calculations with our…

β- and γ-spectroscopy study of 119Pd and 119Ag

Neutron-rich 119Pd nuclei were produced in fission of natural uranium, induced by 25-MeV protons. Fission fragments swiftly extracted with the Ion Guide Isotope Separation On-Line method were mass separated using a dipole magnet and a Penning trap, providing mono-isotopic samples of 119Pd. Their β− decay was measured with γγ- and βγ-spectroscopy methods using low-energy germanium detectors and a thin plastic scintillator. Two distinct nuclear-level structures were observed in 119Ag, based on the 1/2− and 7/2+ isomers reported previously. The β−-decay work was complemented by a prompt-γ study of levels in 119Ag populated in spontaneous fission of 252Cf, performed using the Gammasphere array …

Penning-trap-assisted study of excitations in $^{88}$Br populated in β decay of $^{88}$Se

Excited levels of 88Br populated in the β decay of 88Se have been studied by means of βγ and γ γ spectroscopy methods. Neutron-rich parent 88Se nuclei were produced with proton-induced fission of 238U 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 Jyvaskyl ¨ a. The level scheme ¨ of 88Br has been constructed and log f t values of levels were determined. The ground-state spin of 88Br is now firmly determined to be 1−. Low-energy levels in 88Br were interpreted as members of the πp3/2(νd5/2) 3, πp−1 3/2(νd5/2) 3, πf −1 5/2 (νd5/2) 3, and…

Discovery of an Exceptionally Strong β -Decay Transition of $^{20}$F and Implications for the Fate of Intermediate-Mass Stars

A significant fraction of stars between 7-11 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, due to 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 have established that its strength is exceptionally large and 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 b…

Total absorption γ-ray spectroscopy of the β-delayed neutron emitters 137I and 95Rb

The decays of the β-delayed neutron emitters 137I and 95Rb 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 Jyväskylä 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 s…

Direct determination of the atomic mass difference of the pairs 76As−76Se and 155Tb−155Gd rules out 76As and 155 Tb as possible candidates for electron (anti)neutrino mass measurements

The first direct determination of the ground-state–to–ground-state Q values of the β− decay 76As→76Se and the electron-capture decay 155Tb→155Gd was performed utilizing the double Penning trap mass spectrometer JYFLTRAP. By measuring the atomic mass difference of the decay pairs via the phase-imaging ion-cyclotron-resonance technique, the Q values of 76As→76Se and 155Tb→155Gd were determined to be 2959.265(74) keV and 814.94(18) keV, respectively. The precision was increased relative to earlier measurements by factors of 12 and 57, respectively. The new Q values are 1.33 keV and 5 keV lower compared to the values adopted in the most recent Atomic Mass Evaluation 2020. With the newly determi…

High-precision $Q$-value measurement confirms the potential of $^{135}$Cs for antineutrino-mass detection

The ground-state-to-ground-state $\beta$-decay $Q$-value of $^{135}\textrm{Cs}(7/2^+)\to\,^{135}\textrm{Ba}(3/2^+)$ was directly measured for the first time utilizing the Phase-Imaging Ion-Cyclotron Resonance (PI-ICR) technique at the JYFLTRAP Penning-trap setup. It is the first direct determination of this $Q$-value and its value of 268.66(30)\,keV is a factor of three more precise than the currently adopted $Q$-value in the Atomic Mass Evaluation 2016. Moreover, the $Q$-value deduced from the $\beta$-decay endpoint energy has been found to deviate from our result by approximately 6 standard deviations. The measurement confirms that the first-forbidden unique $\beta^-$-decay transition $^{…

Observation of an ultralow- Q -value electron-capture channel decaying to As 75 via a high-precision mass measurement

Offline commissioning of a new gas cell for the MARA Low-Energy Branch

Results of offline commissioning tests for a new dedicated gas cell for the Mass Analysing Recoil Apparatus (MARA) Low-Energy Branch are reported. Evacuation time, ion survival and transport efficiency in helium buffer gas were characterized with a radioactive 223Ra 𝛼-recoil source. Suppression of the ion signal, originating from non-neutralized species in the gas cell, was explored with 219Rn ions, the daughter recoil of 223Ra, as a function of voltage applied to one of the ion-collector electrodes. Two-step laser resonance ionization of stable tin isotopes produced inside the gas cell from a heated bronze filament was demonstrated, and broadening of the atomic resonances in argon buffer …

Odd-odd neutron-rich rhodium isotopes studied with the double Penning trap JYFLTRAP

Precision mass measurements of neutron-rich rhodium isotopes have been performed at the JYFLTRAP Penning trap mass spectrometer at the Ion Guide Isotope Separator On-Line (IGISOL) facility. We report results on ground- and isomeric-state masses in $^{110,112,114,116,118}$Rh and the very first mass measurement of $^{120}$Rh. The isomeric states were separated and measured for the first time using the phase-imaging ion-cyclotron-resonance (PI-ICR) technique. For $^{112}$Rh, we also report new half-lives for both the ground state and the isomer. The results are compared to theoretical predictions using the BSkG1 mass model and discussed in terms of triaxial deformation.

High-Precision Q-Value Measurement Confirms the Potential of 135Cs for Absolute Antineutrino Mass Scale Determination

The ground-state-to-ground-state β-decay Q value of Cs135(7/2+)→Ba135(3/2+) has been directly measured for the first time. The measurement was done utilizing both the phase-imaging ion-cyclotron resonance technique and the time-of-flight ion-cyclotron resonance technique at the JYFLTRAP Penning-trap setup and yielded a mass difference of 268.66(30) keV between Cs135(7/2+) and Ba135(3/2+). With this very small uncertainty, this measurement is a factor of 3 more precise than the currently adopted Q value in the Atomic Mass Evaluation 2016. The measurement confirms that the first-forbidden unique β--decay transition Cs135(7/2+)→Ba135(11/2-) is a candidate for antineutrino mass measurements wit…

Mass measurements and implications for the energy of the high-spin isomer in 94Ag.

Nuclides in the vicinity of 94Ag have been studied with the Penning trap mass spectrometer JYFLTRAP at the Ion-Guide Separator On-Line. The masses of the two-proton-decay daughter 92Rh and the beta-decay daughter 94Pd of the high-spin isomer in 94Ag have been measured, and the masses of 93Pd and 94Ag 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 94Ag, -46370(170) or -44970(100) keV, corresponding to excitation energies of 6960(400) or 8360(370) keV, respectively.

High-precision Q-value measurement and nuclear matrix element calculations for the double-$$\beta $$ decay of $$^{98}$$Mo

AbstractThe $$^{98}$$ 98 Mo double-beta decay Q-value has been measured, and the corresponding nuclear matrix elements of neutrinoless double-beta ($$0\nu \beta \beta $$ 0 ν β β ) decay and the standard two-neutrino double-beta ($$2\nu \beta \beta $$ 2 ν β β ) decay have been provided by nuclear theory. The double-beta decay Q-value has been determined as $$Q_{\beta \beta }=113.668(68)$$ Q β β = 113.668 ( 68 )  keV using the JYFLTRAP Penning trap mass spectrometer. It is in agreement with the literature value, $$Q_{\beta \beta }=109(6)$$ Q β β = 109 ( 6 )  keV, but almost 90 times more precise. Based on the measured Q-value, precise phase-space factors for $$2\nu \beta \beta $$ 2 ν β β deca…

Revised decay properties of the key 93-keV resonance in the 25Mg(p,γ) reaction and its influence on the MgAl cycle in astrophysical environments

The γ-decay properties of an excited state in 26Al at 6398.3(8) keV have been reexamined using the 11B+16O fusion-evaporation reaction. This level represents a key 93.1(8)-keV resonance in the 25Mg+p system and its relative branching to the 26Al ground state, f0, has been determined to be 0.76±0.03 (stat.) ±0.10 (syst.). This is a significantly higher value than the most recent evaluation and implies a considerable increase in the production of cosmic γ rays from 26Al radioactivity. peerReviewed

Excited states in 87Br populated in β decay of 87Se

Excited levels in 87Br, populated in β decay of 87Se, have been studied by means of γ-ray spectroscopy using an array of broad energy Ge detectors. 87Se nuclei were produced by irradiating a natural Th target with 25-MeV protons. Fission products were extracted from the target chamber using the IGISOL technique, then separated on a dipole magnet and Penning trap (JYFLTRAP) setup. The scheme of excited levels of 87Br has been significantly extended. 114 new transitions and 51 new levels were established. β feedings and log(ft) values of levels were determined. The upper limit for β feeding to the ground state of 87Br was determined to be 23(5)%. Ground state spin and parity 5/2− was confirme…

Direct determination of the excitation energy of the quasistable isomer Ta180m

International audience; Ta180m is a naturally abundant quasistable nuclide and the longest-lived nuclear isomer known to date. It is of interest, among others, for the search for dark matter, for the development of a γ laser, and for astrophysics. So far, its excitation energy has not been measured directly but has been based on an evaluation of available nuclear reaction data. We have determined the excitation energy of this isomer with high accuracy using the Penning-trap mass spectrometer JYFLTRAP. The determined mass difference between the ground and isomeric states of Ta180 yields an excitation energy of 76.79(55) keV for Ta180m. This is the first direct measurement of the excitation e…

Measurement of the 2+→0+ ground-state transition in the β decay of F 20

| openaire: EC/H2020/654002/EU//ENSAR2 We report the first detection of the second-forbidden, nonunique, 2(+) -> 0(+), ground-state transition in the beta decay of F-20. 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 beta spectrum measured using a magnetic transporter and a plastic-scintillator detector. The beta-decay branching ratio inferred from the measurement is b(beta) = [0.41 +/- 0.08(stat) +/- 0.07(sys)] x 10(-5) corresponding to log ft = 10.89(11), making this one of the strongest second-forbidden, nonunique beta transitions ever measured. The experimental result is supported by shell-mode…

Measurement of the 2 + → 0 + ground-state transition in the β decay of F 20

A consistent modification of a test for independence based on the empirical characteristic function

A modification of a test for independence based on the empirical characteristic function is investigated. The initial test is not consistent in the general case. The modification makes the test always consistent and asymptotically distribution free. It is based on a special transformation of the data.

Horizons: Nuclear Astrophysics in the 2020s and Beyond

Nuclear astrophysics is a field at the intersection of nuclear physics and astrophysics, which seeks to understand the nuclear engines of astronomical objects and the origin of the chemical elements. This white paper summarizes progress and status of the field, the new open questions that have emerged, and the tremendous scientific opportunities that have opened up with major advances in capabilities across an ever growing number of disciplines and subfields that need to be integrated.We take a holistic view of the field discussing the unique challenges and opportunities in nuclear astrophysics in regards to science, diversity, education, and the interdisciplinarity and breadth of the field…

First trap-assisted decay spectroscopy of the $$^{81}$$Ge ground state

AbstractThe $$\beta $$ β -delayed $$\gamma $$ γ spectroscopy of $$^{81}$$ 81 As has been performed using a purified beam of $$^{81}$$ 81 Ge $$(9/2^+)$$ ( 9 / 2 + ) ground state at the Ion Guide Isotope Separator On-Line facility (IGISOL). The $$^{81}$$ 81 Ge$$^+$$ + ions were produced using proton-induced fission of $$^{232}$$ 232 Th and selected with the double Penning trap JYFLTRAP for the post-trap decay spectroscopy measurements. The low-spin $$(1/2^+)$$ ( 1 / 2 + ) isomeric-state ions $$^{81m}\hbox {Ge}^+$$ 81 m Ge + were not observed in the fission products. The intrinsic half-life of the $$^{81}$$ 81 Ge ground state has been determined as $$T_{1/2}=6.4(2)~\hbox {s}$$ T 1 / 2 = 6.4 ( …

Novel Penning-trap techniques reveal isomeric states in $^{128}$In and $^{130}$In for the first time

Isomeric states in $^{128}$In and $^{130}$In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing novel ion manipulation techniques, different states were separated and masses of six beta-decaying states were 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 $15^-$ isomer in $^{128}$Sn has been discovered in $^{128}$In 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 $^{130}$In, the lowest-lying $…

Dy 159 Electron-Capture: A New Candidate for Neutrino Mass Determination

Discovery of an Exceptionally Strong β -Decay Transition of F 20 and Implications for the Fate of Intermediate-Mass Stars

First β-decay scheme of 107Nb : New insight into the low-energy levels of 107Mo

Monoisotopic samples of 107Nb nuclei, produced in the proton-induced fission of 238U and separated using the IGISOL mass separator coupled to a Penning trap, were used to perform β- and γ-coincidence spectroscopy of 107Mo. Gamma transitions and excited levels in 107Mo were observed in β decay for the first time. Spin and parity 1/2+ for the ground state of 107Mo is proposed, to replace the previous 5/2+ assignment. The experimental β-decay half-life of 107Nb was estimated to be 0.27±0.02 s. peerReviewed

Mass of astrophysically relevant 31Cl and the breakdown of the isobaric multiplet mass equation

The mass of $^{31}$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, -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 ($\chi^2_n$=11.6) and a non-zero cubic term, d=-3.5(11) keV, is obtained when the new mass value is adopted. $^{31}$Cl has been found to be less proton-bound with a proton separation energy of $S_p$=265(4) keV. Energies for the excited states in $^{31}$Cl and the photodisintegration rate on $^{31}$Cl have been determined with s…

Three beta-decaying states in In and In resolved for the first time using Penning-trap techniques

Isomeric states in $^{128}$In and $^{130}$In 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 $^{128}$In and $^{130}$In 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 15− isomer in $^{128}$Sn has been discovered in $^{128}$In 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 …

Direct determination of the atomic mass difference of the pairs As76−Se76 and Tb155−Gd155 rules out As76 and Tb155 as possible candidates for electron (anti)neutrino mass measurements

Direct measurement of the mass difference of As 72 − Ge 72 rules out As 72 as a promising β -decay candidate to determine the neutrino mass

β - and γ -spectroscopy study of Pd 119 and Ag 119

Precision mass measurements of 67Fe and 69,70Co: Nuclear structure toward N = 40 and impact on r-process reaction rates

Accurate mass measurements of neutron-rich iron and cobalt isotopes 67Fe and 69,70Co have been realized with the JYFLTRAP double Penning-trap mass spectrometer. With novel ion-manipulation techniques, the masses of the 69,70Co ground states and the 1/2− isomer in 69Co 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 68Ni, a region known for shape coexistence and increased collectivity. The excitation energy for the 1/2− intruder state in 69Co has been determined for the first time and is compared to lar…

TAS measurements for reactor physics and nuclear structure

In this contribution we will present recent total absorption measurements of the beta decay of neutron‐rich nuclei performed at the IGISOL facility of the Univ. of Jyvaskyla. In the measurements the JYFL Penning Trap was used as a high resolution isobaric separator. The total absorption technique will be described and the impact of recent results in the fields of reactor physics (decay heat calculations) and nuclear structure will be discussed.

New constraints on the Al 25 (p,γ) reaction and its influence on the flux of cosmic γ rays from classical nova explosions

The astrophysical Al25(p,γ)Si26 reaction represents one of the key remaining uncertainties in accurately modeling the abundance of radiogenic Al26 ejected from classical novae. Specifically, the strengths of key proton-unbound resonances in Si26, that govern the rate of the Al25(p,γ) reaction under explosive astrophysical conditions, remain unsettled. Here, we present a detailed spectroscopy study of the Si26 mirror nucleus Mg26. We have measured the lifetime of the 3+, 6.125-MeV state in Mg26 to be 19(3)fs and provide compelling evidence for the existence of a 1- state in the T=1,A=26 system, indicating a previously unaccounted for=1 resonance in the Al25(p,γ) reaction. Using the presently…

Benchmark of a multi-physics Monte Carlo simulation of an ionguide for neutron-induced fission products

AbstractTo enhance the production of medium-heavy, neutron-rich nuclei, and to facilitate measurements of independent yields of neutron-induced fission, a proton-to-neutron converter and a dedicated ion guide for neutron-induced fission have been developed for the IGISOL facility at the University of Jyväskylä. The ion guide holds the fissionable targets, and the fission products emerging from the targets are collected in helium gas and transported to the downstream experimental stations. A computer model, based on a combination of MCNPX for modeling the neutron production, the fission code GEF, and GEANT4 for the transport of the fission products, was developed. The model will be used to i…

Mass measurements towards doubly magic Ni-78 : Hydrodynamics versus nuclear mass contribution in core-collapse supernovae

International audience; We report the first high-precision mass measurements of the neutron-rich nuclei 74,75Ni and the clearly identified ground state of 76Cu, along with a more precise mass-excess value of 78Cu, performed with the double Penning trap JYFLTRAP at the Ion Guide Isotope Separator On-Line (IGISOL) facility. These new results lead to a quantitative estimation of the quenching for the N=50 neutron shell gap. The impact of this shell quenching on core-collapse supernova dynamics is specifically tested using a dedicated statistical equilibrium approach that allows a variation of the mass model independent of the other microphysical inputs. We conclude that the impact of nuclear m…

Dy159 Electron-Capture: A New Candidate for Neutrino Mass Determination

Electron-capture branch of 100Tc and tests of nuclear wave functions for double-beta decays

We present a measurement of the electron-capture branch of $^{100}$Tc. Our value, $B(\text{EC}) = (2.6 \pm 0.4) \times 10^{-5}$, implies that the $^{100}$Mo neutrino absorption cross section to the ground state of $^{100}$Tc is roughly one third larger than previously thought. Compared to previous measurements, our value of $B(\text{EC})$ prevents a smaller disagreement with QRPA calculations relevant to double-$\beta$ decay matrix elements.

Study of the Ti-44(alpha, p)V-47 reaction and implications for core collapse supernovae

The underlying physics triggering core collapse supernovae is not fully understood but observations of material ejected during such events helps to solve this puzzle. In particular, several satellite based γ -ray observations of the isotope 44Ti have been reported recently. Conveniently, the amount of this isotope in stellar ejecta is thought to depend critically on the explosion mechanism. The most influential reaction to the amount of 44Ti in supernovae is 44Ti(α, p)47V. Here we report on a direct study of this reaction conducted at the REX-ISOLDE facility, CERN. The experiment was performed with a 44Ti beam at Elab = 2.16 MeV/u, corresponding to an energy distribution, for reacting α-par…

β decay of Cd 127 and excited states in In 127

22 pags., 8 figs., 4 tabs., 1 app.