0000000000302417
AUTHOR
V.-v. Elomaa
Experimental studies at JYFLTRAP
JYFLTRAP is a Penning trap system at the accelerator laboratory in Jyvaskyla, Finland that enables high-precision experiments with stored, exotic species that are produced at the IGISOL facility. On one hand, these can be performed within the trap itself, like e.g. mass spectrometry. On the other hand, the trap can be used to provide the highly purified species for further experiments, e.g. for trap-assisted nuclear decay spectroscopy. This contribution focuses on these two possible applications with the presentation of some recent results on superallowed beta decays.
Signatures of oblate deformation in the ^{111}Tc nucleus
Monoisotopic samples of exotic, neutron-rich ${}^{111}$Mo nuclei, produced in the deuteron-induced fission of ${}^{238}$U and separated using the IGISOL3 isotope separator, coupled to the JYFLTRAP Penning trap, were used to perform $\ensuremath{\beta}$- and $\ensuremath{\gamma}$-coincidence spectroscopy of ${}^{111}$Tc. New excited levels in ${}^{111}$Tc populated in ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of ${}^{111}$Mo provide the first indication for an oblate deformation in the mass $A\ensuremath{\approx}110$ region. The wide spin range of levels populated in ${}^{111}$Tc following the decay of ${}^{111}$Mo indicates the existence of two $\ensuremath{\beta}$-decaying levels in ${…
Mass ofAl23for testing the isobaric multiplet mass equation
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].
Smallest KnownQValue of Any Nuclear Decay: The Rareβ−Decay ofIn115(9/2+)→Sn115(3/2+)
The ground-state-to-ground-state Q_{beta;{-}} value of ;{115}In was determined to 497.68(17) keV using a high-precision Penning trap facility at the University of Jyvaskyla, Finland. From this, a Q_{beta;{-}} value of 0.35(17) keV was obtained for the rare beta;{-} decay to the first excited state of ;{115}Sn at 497.334(22) keV. The partial half-life was determined to 4.1(6) x 10;{20} yr using ultra low-background gamma-ray spectrometry in an underground laboratory. Theoretical modeling of this 2nd-forbidden unique beta;{-} transition was also undertaken and resulted in Q_{beta;{-}} = 57_{-12};{+19} eV using the measured half-life. The discrepancy between theory and experiment could be attr…
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.
Precision mass measurements of neutron-rich Tc, Ru, Rh, and Pd isotopes
The masses of neutron-rich $^{106\ensuremath{-}112}\mathrm{Tc}$, $^{106\ensuremath{-}115}\mathrm{Ru}$, $^{108\ensuremath{-}118}\mathrm{Rh}$, and $^{112\ensuremath{-}120}\mathrm{Pd}$ produced in proton-induced fission of uranium were determined using the JYFLTRAP double Penning trap setup. The measured isotopic chains include a number of previously unmeasured nuclei. Typical precisions on the order of 10 keV or better were achieved, representing a factor of 10 improvement over earlier data. In many cases, significant deviations from the earlier measurements were found. The obtained data set of 39 masses is compared with different mass predictions and analyzed for global trends in the nuclear…
Independent Isotopic Product Yields in 25 MeV and 50 MeV Charged Particle Induced Fission of 238U and 232Th
Abstract Independent isotopic yields for most elements from Zn to La in 25-MeV proton-induced fission of 238U and 232Th have been determined at the IGISOL facility in the University of Jyvaskyla. In addition, isotopic yields for Zn, Ga, Rb, Sr, Zr, Pd and Xe in 50-MeV proton-induced fission of 238U and for Zn, Ga, Rb, Sr, Cd and In in 25-MeV deuterium-induced fission of 238U have been measured. The utilised technique recently developed at the University of Jyvaskyla, is based on a combination of the ion guide technique and the ability of a Penning trap to unambiguously identify the isotopes by their atomic mass. Since the yields are determined by ion counting, no prior knowledge beyond the …
Mass measurements in the vicinity of the doubly magic waiting pointNi56
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 dete…
Strong γ-ray emission from neutron unbound states populated in β-decay: Impact on (n,γ) cross-section estimates
J. L. Taín et al. -- 6 pags., 7 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0
Accurate Q value for the 74Se double-electron-capture decay
Abstract 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…
Total Absorption Spectroscopy of Fission Fragments Relevant for Reactor Antineutrino Spectra and Decay Heat Calculations
Volume: 111 Host publication title: WONDER-2015 Host publication sub-title: 4TH INTERNATIONAL WORKSHOP ON NUCLEAR DATA EVALUATION FOR REACTOR APPLICATIONS Isbn(print): 978-2-7598-1970-6 Beta decay of fission products is at the origin of decay heat and antineutrino emission in nuclear reactors. Decay heat represents about 7% of the reactor power during operation and strongly impacts reactor safety. Reactor antineutrino detection is used in several fundamental neutrino physics experiments and it can also be used for reactor monitoring and non-proliferation purposes. Rb-92,Rb-93 are two fission products of importance in reactor antineutrino spectra and decay heat, but their beta-decay properti…
Electron-capture branch ofTc100and tests of nuclear wave functions for double-βdecays
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 JYFLTRAP control and measurement system
The JYFLTRAP setup has been used for precision mass spectrometry since 2003. An essential part of this setup is the computer-controlled system consisting of software and hardware that is required to operate the instruments. The software has been developed solely at JYFL using LabVIEW and C++ development tools. The hardware consists of devices controlled using Control Area Network (CAN) field bus and Ethernet for communication purposes. LAN/GPIB-gateways, modular multichannel ISEG DC power supplies and WAGO I/O systems are also used.
$Q$-value of the superallowed $\beta$ decay of 62Ga
Masses of the radioactive isotopes 62Ga, 62Zn and 62Cu have been measured at the JYFLTRAP facility with a relative precision of better than 18 ppb. A Q_EC value of (9181.07 +- 0.54) keV for the superallowed decay of 62Ga is obtained from the measured cyclotron frequency ratios of 62Ga-62Zn, 62Ga-62Ni and 62Zn-62Ni ions. The resulting Ft-value supports the validity of the conserved vector current hypothesis (CVC). The mass excess values measured were (-51986.5 +-1.0) keV for 62Ga, (-61167.9 +- 0.9) keV for 62Zn and (-62787.2 +- 0.9) keV for 62Cu.
Upgrade and yields of the IGISOL facility
The front end of the Jyvaskyla IGISOL facility was upgraded in 2003 by increasing its pumping capacity and by improving the radiation shielding. In late 2005, the skimmer electrode of the mass separator was replaced by a sextupole ion guide, which improved the mass separator efficiency up to an order of magnitude. The current design of the facility is described. The updated yield data, achieved with and without the additional JYFLTRAP purification, using both fusion evaporation reactions and particle induced fission is presented to give an overview of the capability of the facility. These data have been determined either by radioactivity measurements or by direct ion counting after the Penn…
Half-life, branching-ratio, andQ-value measurement for the superallowed0+→0+β+emitterTi42
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-lif…
β-decay data requirements for reactor decay heat calculations: study of the possible source of the gamma-ray discrepancy in reactor heat summation calculations
The decay heat of fission products plays an important role in predictions of the heat up of nuclear fuel in reactors. The released energy is calculated as the summation of the activities of allfission products P(t) = Ei λi Ni(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 in the t ∼ 1000s cooling time for some fuels. A possible explanation to this improper description has been found in the work of Yoshida et al. (1), where it has been shown that…
Q values of the 76Ge and 100Mo double-beta decays
Abstract 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.
Precision mass measurements of neutron-rich yttrium and niobium isotopes
Abstract The atomic masses of neutron-rich 95–101 Y and 101–107 Nb produced in proton-induced fission of uranium were determined using the JYFLTRAP double Penning trap setup. Accuracies of better than 10 keV could be reached for most nuclides. The masses of 106,107 Nb were measured for the first time. The energies of the isomeric states in 96 Y and 100 Y were measured as 1541(10) keV and 145(15) keV. The niobium isotopes appear to be systematically less bound than the values given in the latest Atomic Mass Evaluation. The new data lie in a region of the nuclear chart characterised by the transition from spherical to strongly deformed shapes. These structural changes are explored by studying…
Penning-trap-assisted study of 115Ru beta decay
The beta decay of 115Ru has been studied by means of Penning-trap-assisted beta and gamma spectroscopy at the IGISOL facility. The level scheme of 115Rh has been substantially extended and compared with the level systematics of lighter rhodium isotopes. Tentative candidates for three states of the deformed K = 1/2 band have been suggested. The beta-strength distribution of the beta decay of 115Ru differs from the beta decays of 111, 113, 113mRu isotopes due to non-observation of the 3-quasiparticle states in 115Rh. The decay properties of 115Ru indicate a spin-parity of (3/2+ for its beta-decaying ground state. In addition, possible Nilsson states as well as the shape and spin transitions i…
Mass Measurements and Implications for the Energy of the High-Spin Isomer inAg94
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.
Excited states inPd115populated in theβ−decay ofRh115
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.
Reactor Decay Heat inPu239: Solving theγDiscrepancy in the 4–3000-s Cooling Period
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.
Decay study ofTc114with a Penning trap
The level structure of $^{114}\mathrm{Ru}$ has been investigated via the $\ensuremath{\beta}$ decay of very neutron-rich $^{114}\mathrm{Tc}$ by means of Penning-trap-assisted $\ensuremath{\gamma}$ spectroscopy. The deduced $\ensuremath{\beta}$-decay scheme suggests the existence of two $\ensuremath{\beta}$-decaying states in $^{114}\mathrm{Tc}$ with ${I}^{\ensuremath{\pi}}={1}^{+}$ and $I\ensuremath{\geqslant}$ 4, with half-lives of ${t}_{1/2}({1}^{+})=90(20)$ ms and ${t}_{1/2}(I\ensuremath{\geqslant}4)=100(20)$ ms, respectively. The ${Q}_{\ensuremath{\beta}}$ value, which covers a possible mixture of two states, has been determined to be ${Q}_{\ensuremath{\beta}}=11 785(12)$ keV. The level…
QValues of the SuperallowedβEmittersAlm26,Sc42, andV46and Their Impact onVudand the Unitarity of the Cabibbo-Kobayashi-Maskawa Matrix
The $\ensuremath{\beta}$-decay ${Q}_{\mathrm{EC}}$ values of the superallowed beta emitters $^{26}\mathrm{Al}^{m}$, $^{42}\mathrm{Sc}$, and $^{46}\mathrm{V}$ have been measured with a Penning trap to a relative precision of better than $8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$. Our result for $^{46}\mathrm{V}$, 7052.72(31) keV, confirms a recent measurement that differed from the previously accepted reaction-based ${Q}_{\mathrm{EC}}$ value. However, our results for $^{26}\mathrm{Al}^{m}$ and $^{42}\mathrm{Sc}$, 4232.83(13) keV and 6426.13(21) keV, are consistent with previous reaction-based values. By eliminating the possibility of a systematic difference between the two t…
Systematic studies of the accuracy of the Penning trap mass spectrometer JYFLTRAP
Abstract Measurements to quantify the mass-dependent systematic effect and the residual uncertainty of the JYFLTRAP setup have been performed with carbon-cluster ions. The primary quantities reported in this work are a mass-dependent uncertainty of σ m ( r ) / r = ( 7.8 ± 0.3 × 10 - 10 / u ) × Δ m and a residual uncertainty of σ res ( r ) / r = 1.2 × 10 - 8 for the JYFLTRAP mass spectrometer. By restricting the mass difference between the reference ion and ion of interest to | m meas - m ref | ≤ 24 , the values for the mass-dependent effect and the corresponding residual uncertainty are σ m , lim ( r ) / r = ( 7.5 ± 0.4 × 10 - 10 / u ) × Δ m and σ res , lim ( r ) / r = 7.9 × 10 - 9 , respec…
Total Absorption Spectroscopy Study ofRb92Decay: 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 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.
Improvements on Decay Heat Summation Calculations by Means of Total Absorption Gamma-ray Spectroscopy Measurements
The decay heat of fission products plays an important role in predictions of the heat released by nuclear fuel in reactors. In this contribution we present results of the analysis of the measurement of the beta decay of some refractory isotopes that were considered possible important contributors to the decay heat in reactors. The measurements presented here were performed at the IGISOL facility of the University of Jyvaeskylae, Finland. In our measurements we have combined for the first time a Penning trap (JYFLTRAP), which was used as a high resolution isobaric separator, with a total absorption spectrometer. The results of the measurements as well as their consequences for decay heat sum…
Masses of neutron-rich Ni and Cu isotopes and the shell closure at Z = 28 , N = 40
The Penning trap mass spectrometer JYFLTRAP, coupled to the Ion Guide Isotope Separator On-Line (IGISOL) facility at Jyvaskyla, was employed to measure the atomic masses of neutron-rich 70-73Ni and 73, 75Cu isotopes with a typical accuracy less than 5keV. The mass of 73Ni was measured for the first time. Comparisons with the previous data are discussed. Two-neutron separation energies show a weak subshell closure at 68 28Ni40 . A well established proton shell gap is observed at Z = 28 .
Preparing isomerically pure beams of short-lived nuclei at JYFLTRAP
A new procedure to prepare isomerically clean samples of ions with a mass resolving power of more than 100,000 has been developed at the JYFLTRAP tandem Penning trap system. The method utilises a dipolar rf-excitation of the ion motion with separated oscillatory fields in the precision trap. During a subsequent retransfer to the purification trap, the contaminants are rejected and as a consequence, the remaining bunch is isomerically cleaned. This newly-developed method is suitable for very high-resolution cleaning and is at least a factor of five faster than the methods used so far in Penning trap mass spectrometry.
Enhancedγ-Ray Emission from Neutron Unbound States Populated inβDecay
Total absorption spectroscopy is used to investigate the β-decay intensity to states above the neutron separation energy followed by γ-ray emission in (87,88)Br and (94)Rb. Accurate results are obtained thanks to a careful control of systematic errors. An unexpectedly large γ intensity is observed in all three cases extending well beyond the excitation energy region where neutron penetration is hindered by low neutron energy. The γ branching as a function of excitation energy is compared to Hauser-Feshbach model calculations. For (87)Br and (88)Br the γ branching reaches 57% and 20%, respectively, and could be explained as a nuclear structure effect. Some of the states populated in the daug…
Double-beta decay Q values of 116Cd and 130Te
Abstract 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 …
Development of a carbon-cluster ion source for JYFLTRAP
Abstract A carbon-cluster ion source based on laser ablation and ionization of a carbon sample has been built and tested for the JYFLTRAP setup. In the present configuration the ion source is situated in the electrostatic switchyard in front of the radiofrequency (RFQ) cooler and buncher. In this position the beam quality of the carbon clusters injected into the Penning trap system is considerably improved by the RFQ. Moreover, the mass-dependence of the RFQ’s transmission can be used to some extent to suppress unwanted cluster sizes.
Trap-assisted separation of nuclear states for gamma-ray spectroscopy: the example of100Nb
Low-lying levels in 100Mo are known to be populated by beta decay from both the ground and isomeric states in 100Nb. The small energy difference (~3 ppm) between the two parent states and the similarity of their half-lives make it difficult to distinguish experimentally between the two decay paths. A new technique for separating different states of nuclei has recently been developed in a series of experiments at the IGISOL facility, using the JYFLTRAP installation, at the University of Jyvaskyla where mass resolution ~2 ppm was achieved in mass measurements and in the production of 133mXe. This paper reports on the extension of this technique to allow the separate study of the gamma-ray dec…
Ultra-high resolution mass separator—Application to detection of nuclear weapons tests
Abstract A Penning trap-based purification process having a resolution of about 1 ppm is reported. In this context, we present for the first time a production method for the most complicated and crucially important nuclear weapons test signature, 133mXe. These pure xenon samples are required by the Comprehensive Nuclear-Test-Ban Treaty Organization to standardize and calibrate the worldwide network of xenon detectors.
An ion guide for the production of a low energy ion beam of daughter products of α-emitters
A new ion guide has been modeled and tested for the production of a low energy ($\approx$ 40 kV) ion beam of daughter products of alpha-emitting isotopes. The guide is designed to evacuate daughter recoils originating from the $\alpha$-decay of a $^{233}$U source. The source is electroplated onto stainless steel strips and mounted along the inner walls of an ion guide chamber. A combination of electric fields and helium gas flow transport the ions through an exit hole for injection into a mass separator. Ion guide efficiencies for the extraction of $^{229}$Th$^{+}$ (0.06%), $^{221}$Fr$^{+}$ (6%), and $^{217}$At$^{+}$ (6%) beams have been measured. A detailed study of the electric field and …
New isomer and decay half-life ofRu115
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 $\mathit{oblate}$ $3/{2}^{+}$…
Total absorption spectroscopy study of the β decay of Br86 and Rb91
The beta decays of 86Br and 91Rb have been studied using the total absorption spectroscopy technique. The radioactive nuclei were produced at the IGISOL facility in Jyvaskyla and further purified using the JYFLTRAP. 86Br and 91Rb are considered high priority contributors to the decay heat in reactors. In addition 91Rb was used as a normalization point in direct measurements of mean gamma energies released in the beta decay of fission products by Rudstam et al. assuming that this decay was well known from high-resolution measurements. Our results shows that both decays were suffering from the Pandemonium effect and that the results of Rudstam et al. should be renormalized.
AccurateQValue for theSn112Double-βDecay and its Implication for the Search of the Neutrino Mass
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 $^{112}\mathrm{Cd}$.