Search

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.

International audience; Total absorption gamma-ray spectroscopy is used to measure accurately the intensity of γ emission from neutron-unbound states populated in the β-decay of delayed-neutron emitters. From the comparison of this intensity with the intensity of neutron emission a constraint on the (n, γ) cross section for highly unstable neutron-rich nuclei can be deduced. A surprisingly large γ branching was observed for a number of isotopes which might indicate the need to increase by a large factor the Hauser-Feshbach (n, γ) cross-section estimates that impact on r process abundance calculations.

We investigate the decay of 87,88Br and 94Rb using total absorption γ -ray spectroscopy. These important fission products are β-delayed neutron emitters. Our data show considerable βγ intensity, so far unobserved in high-resolution γ -ray spectroscopy, from states at high excitation energy. We also find significant differences with the β intensity that can be deduced from existing measurements of the β spectrum. We evaluate the impact of the present data on reactor decay heat using summation calculations. Although the effect is relatively small it helps to reduce the discrepancy between calculations and integral measurements of the photon component for 235U fission at cooling times in the range 1–100 s. We also use summation calculations to evaluate the impact of present data on reactor antineutrino spectra. We find a significant effect at antineutrino energies in the range of 5 to 9 MeV. In addition, we observe an unexpected strong probability for γ emission from neutron unbound states populated in the daughter nucleus. The γ branching is compared to Hauser-Feshbach calculations, which allow one to explain the large value for bromine isotopes as due to nuclear structure. However the branching for 94Rb, although much smaller, hints of the need to increase the radiative width γ by one order of magnitude. This increase in γ would lead to a similar increase in the calculated (n,γ ) cross section for this very neutron-rich nucleus with a potential impact on r process abundance calculations.

J. L. Taín et al. -- 6 pags., 7 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0, Total absorption gamma-ray spectroscopy is used to measure accurately the intensity of ¿ emission from neutron-unbound states populated in the ß-decay of delayed-neutron emitters. From the comparison of this intensity with the intensity of neutron emission one can deduce information on the (n,¿) cross section for unstable neutron-rich nuclei of interest in r process abundance calculations. A surprisingly large ¿ branching was observed for a number of isotopes. The results are compared with Hauser-Feshbach calculations and discussed., This work was supported by Spanish Ministerio de Economía y Competitividad under grants FPA2008-06419, FPA2010- 17142, FPA2011-24553, FPA2014-52823-C2-1-P, CPAN CSD- 2007-00042 (Ingenio2010) and the program Severo Ochoa (SEV-2014-0398). WG would like to thank the University of Valencia for support. This work was supported by the Academy of Finland under the Finnish Centre of Excellence Programme 2012-2017 (Project No. 21350). Work supported by EPSRC(UK) and STFC(UK) and the UK National Measurement Office. Work supported by the European Commission under the FP7/EURATOM contract 605203. FGK acknowledges support from the U.S. Department of Energy, under contract number DEAC02- 06CH11357.

Preliminary results from beta decay studies of nuclei that are important for reactor applications are presented. The beta decays have been studied using the total absorption technique (TAS) and the pure beams provided by the JYFLTRAP system at the IGISOL facility of the University of Jyväskylä. peerReviewed

The β-decay of 102Sn was studied by using high-resolution germanium detectors as well as a Total Absorption Spectrometer (TAS). A decay scheme has been constructed based on the γ-γ coincidence data. The total experimental Gamow-Teller strength B GT exp of 102Sn was deduced from the TAS data to be 4.2(9). A search for β-delayed γ-rays of 100Sn decay remained unsuccessful. However, a Gamow-Teller hindrance factor h=2:2(3), and a cross-section of about 3 nb for the production of 100Sn in fusion-evaporation reaction between 58Ni beam and 50Cr target have been estimated from the data on heavier tin isotopes. The estimated hindrance factor is similar to the values derived for lower shell nuclei.

The α-decays of 110Xe and 106Te were studied at the GSI on-line mass separator. By using the grow-in and decay of the α activity, observed in pulsed-beam measurement, the half-life of 110Xe was found to be T1/2 = 105+35-25ms. The lifetime of 106Te was determined to be T1/2 = 70+20-10μs by measuring the time between two successive 110Xe →{106} Te →{102} Sn α-decays. The newly determined half-lives were used to calculate reduced α-decay widths for 106Te and 110Xe. Universal systematics of reduced α widths are proposed to search for the evidence of enhancement of the α formation amplitude in the emitters above 100Sn.

Beta decays of 94,96Ag and 103Sn nuclei into proton channels have been studied in the recent experiments at the GSI-ISOL facility. New efficient and chemically selective ion sources provided the highest yields of light silver and tin isotopes. Large arrays of germanium γ-ray and silicon charged-particle detectors, as well as a total absorption spectrometer (TAS) were used to measure β-proton, proton-γ, β-proton-γ and proton-γ-γ spectra. For the decay of 94Ag, we observed high-spin states in 93Rh populated by proton emission following β decay, whose largest spin value (≥39/2) yields an experimental proof for the existence of a second high-spin isomer in 94Ag with I≥17. Its β-decay energy is at least 16.8 MeV, corresponding to an excitation energy ≥5.5 MeV. For 103Sn, the γ rays measured in coincidence with β-delayed protons allowed us to establish the β-decay properties of this isotope. In particular, a QEC value of 7.5(6) MeV is derived from the intensity ratio of protons that are preceded either by EC or by β+ decays and populate the 2+ state in 102Cd.

International audience; The accurate determination of reactor antineutrino spectra remains a very active research topic for which new methods of study have emerged in recent years. Indeed, following the long-recognized reactor anomaly (measured antineutrino deficit in short baseline reactor experiments when compared with spectral predictions), the three international reactor neutrino experiments Double Chooz, Daya Bay and Reno have recently demonstrated the existence of spectral distortions in their measurements with respect to the same predictions. These spectral predictions were obtained through the conversion of integral beta-energy spectra obtained at the ILL research reactor. Several studies have shown that the underlying nuclear physics required for the conversion of these spectra into antineutrino spectra is not totally understood. An alternative to such converted spectra is a complementary approach that consists of determining the antineutrino spectrum by means of the measurement and processing of nuclear data. The beta properties of some key fission products suffer from the pandemonium effect which can be circumvented by the use of the Total Absorption Gamma-ray Spectroscopy technique (TAGS). The two main contributors to the Pressurized Water Reactor antineutrino spectrum in the region where the spectral distortion has been observed are 92Rb and 142Cs, which have been measured at the radioactive beam facility of the University of Jyväskylä in two TAGS experiments. We present the results of the analysis of the TAGS measurements of the β-decay properties of 92Rb along with preliminary results on 142Cs and report on the measurements already performed.

The rare-earth region of the nuclear table around the quasi-doubly magic nucleus $^{146}\text{Gd}$ is one of the very few places in which the Gamow-Teller (GT) resonance can be populated in $\ensuremath{\beta}$ decay. The appropriate technique to study such a phenomenon is total absorption spectroscopy, thanks to which one can measure the $B$(GT) distribution in $\ensuremath{\beta}$-decay experiments even when it is very fragmented and lies at high excitation energy in the daughter nucleus. Results on the GT resonance measured in the $\ensuremath{\beta}$ decay of the odd-$Z, N=83$ nuclei $^{148}\text{Tb}, ^{150}\text{Ho}$, and $^{152}\text{Tm}$ are presented in this work and compared with shell-model calculations. The tail of the resonance is clearly observed up to the limit imposed by the $Q$ value. This observation is important in the context of the understanding of the ``quenching'' of the GT strength.

The energy associated with the decay of fission products plays an important role in the estimation of the amount of heat released by nuclear fuel in reactors. In this article we present results of the study of the beta decay of some refractory isotopes that were considered important contributors to the decay heat in reactors. The measurements were performed at the IGISOL facility of the University of Jyvaskyla, Finland. In these studies 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 summation calculations are discussed.

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 summation calculations are discussed.

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 daughter can only decay through the emission of a large orbital angular momentum neutron with a strongly reduced barrier penetrability. In the case of neutron-rich (94)Rb the observed 4.5% branching is much larger than the calculations performed with standard nuclear statistical model parameters, even after proper correction for fluctuation effects on individual transition widths. The difference can be reconciled by introducing an enhancement of 1 order of magnitude in the photon strength to neutron strength ratio. An increase in the photon strength function of such magnitude for very neutron-rich nuclei, if it proves to be correct, leads to a similar increase in the (n,γ) cross section that would have an impact on r process abundance calculations.

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 daughter can only decay through the emission of a large orbital angular momentum neutron with a strongly reduced barrier penetrability. In the case of neutron-rich (94)Rb the observed 4.5% branching is much larger than the calculations performed with standard nuclear statistical model parameters, even after proper correction for fluctuation effects on individual transition widths. The difference can be reconciled by introducing an enhancement of 1 order of magnitude in the photon strength to neutron strength ratio. An increase in the photon strength function of such magnitude for very neutron-rich nuclei, if it proves to be correct, leads to a similar increase in the (n,γ) cross section that would have an impact on r process abundance calculations.

The masses of 80, 81, 82, 83Y, 83, 84, 85, 86, 88Zr and 85, 86, 87, 88Nb have been measured with a typical precision of 7keV by using the Penning trap setup at IGISOL. The mass of 84Zr has been measured for the first time. These precise mass measurements have improved Sp and QEC values for astrophysically important nuclides.

The β decay of 94Pd and of the 71s isomer of 94Rh was investigated by using total γ-ray absorption techniques. Several levels in 94Rh are established, including a new low-lying isomer characterized by a half-life of 0.48(3)μs and a de-exciting transition of 55keV. E2 multipolarity is determined for this transition by measuring the intensities of its γ-rays and the characteristic X-rays from its electron conversion. On the basis of the measured reduced β-decay transition rates to known 94Ru levels and shell model considerations, the spin-parity of the 71s and the 0.48μs isomers of 94Rh is assigned to be (4+) and (2+), respectively. The β-decay strength distributions measured for 94Pd and the 71s isomer of 94Rh yield Q EC values of 6700(320) and 9750(320)keV for these decays and give evidence for the population of those states below and above the magic N = 50 gap that belong to both components of the 0g spin-orbit doublet.

The β-decay of 105Sn was re-investigated at the ISOL facility of GSI Darmstadt by using a total absorption spectrometer. The experimental results include the half-life and β-delayed proton branching ratio of 32.7(5)s and 1.1(4) . 10-4, respectively, and the contribution of electron capture to the 105Sn decay of 0.420(35). The Gamow-Teller strength distribution peaking at 3.6MeV was measured, yielding a summed Gamow-Teller strength of 3.0(4). The latter data are discussed in comparison with shell-model predictions based on an empirical interaction.

Within a programme of measuring QEC, QEC − Sp and Sp values of nuclei in the 100Sn region, the QEC value of 105Sn was determined to be 6230 (80) keV. This result was obtained by means of the total-absorption spectrometer at the On-line Mass Separator of GSI Darmstadt. Other decay Q-values of nuclei near 100Sn, measured at this facility by investigating positron, electron-capture, β-delayed proton as well as direct proton and α-decay, are also presented. The accuracy of these data ranges from 30 to 260 keV, is thus lower than that obtained by other methods but still sufficient concerning most of the current nuclear-structure studies. Moreover, the determination of Q-values by means of decay measurements has an unrivalled sensitivity.

A new way of study the reaction of triple radiative capture αα(n,γ)9Be is demonstrated. At the GSI-ISOL facility, we have measured the γ decays of excited 1/2+, 5/2− and 1/2− states in 9Be, which are strongly populated in the β decay of 9Li. The respective partial γ-widths are of astrophysical interest in order to reliably estimate the αα(n,γ)9Be rates in SN type-II as a possible site of the synthesis of heavy elements in the Universe. The 9Li nuclei were implanted into a foil viewed by high-granularity arrays of β and γ detectors. The γ-ray spectra were measured in coincidence with the β-particles by selecting large β-γ angles in order to suppress the bremsstrahlung background. For the first time, the γ-rays from the 1/2+ and 5/2− states in 9Be were observed in 9Li decay, with the 1/2+-state energy and width measured to be 1689(10) and 224(7) keV, respectively, while the latter transition provided a reference point. The upper limit of the 1/2− partial γ-width is measured to be 7 ⋅ 10 6 MeV . An improved sensitivity experiment is feasible at facilities with the larger yield of 9Li.

The very neutron-deficient 117Ba nuclei were produced in 58Ni-induced reactions on a 63Cu target and selected for spectroscopic studies by using BaF+ molecules formed in the ion source of the GSI on-line mass separator. The β-decay of 117Ba was investigated by means of the total absorption γ-ray spectrometer and a telescope for β-delayed particle detection. In the analysis combining the β-delayed γ-ray and proton data the energy window available for β-delayed proton emission, the branching ratios for proton transitions to the 116Xe levels and the β-feeding of the γ-ray and proton-emitting 117Cs states were determined. The β-strength function for 117Ba derived from the measured β-feeding distribution revealed the existence of a broad resonance structure at 117Cs excitation energy of about 4-5 MeV. The results of the β-delayed proton studies and β-strength measurements are confronted with theoretical predictions.

One of the main motivations of today’s β-decay studies is to investigate whether the presence of many bound nucleons affects the value of the Gamow—Teller (GT) axialvector coupling constant. The quest for 100Sn is driven by the hope that its particulary simple decay scheme may help to perform improved tests of the models used to calculate the summed GT strength (B GT). Since 100Sn can not yet be produced in sufficient quantity, the experiments are restricted to nearby nuclei. In this paper we report on a study of the β decay of 102In, performed at the GSI Online Mass Separator. This odd—odd nucleus has a very complicated decay scheme and thus represents indeed a great challenge. The loss of numerous weak transitions in high resolution mesurements is suspected to be one of the main reasons for incomplete B GT measurements. Therefore, the experiment with a cube-like array of 6 Euroball Cluster high-resolution germanium detectors (Euroball Cube), with 7 crystals per Cluster, was complemented by the measurement with a total-absorption gamma spectrometer (TAS) [1].

4 pages, 3 figures.-- PACS nr.: 23.40.-s.-- Printed version published Apr 2004.-- et al., Beta-decay experiments are a primary source of information for nuclear-structure studies and at the same time complementary to in-beam investigations of nuclei far from stability. Although both types of experiment are mainly based on γ-ray spectroscopy, they face different experimental problems. The so-called Pandemonium effect is a critical problem in β-decay if we are to test theoretically calculated transition probabilities. In this contribution we will present a solution to this problem using total absorption spectroscopy methods. We will also present some examples of experiments carried out with the Total Absorption Spectrometer (TAS) at GSI an describe a new device LUCRECIA recently installed at CERN., This work was partially supported by C.I.C.Y.T. (Spain) under contract AEN96-1662, by MCYT (Spain)contract No. FPA2002-04181-C04-03, by C.S.R. (Poland) grant KBN-2Pp03B-039-13, by R.F.B.R. (Russia)-D.F.G. (Germany) contract 436 RUS 113/201/0(R). Support from the HPMF-CT-1999-00394 project as well as from the European Large Scale Facility program at CERN is also aknowledged.

The Gamow–Teller β decays of the neutron-deficient indium isotopes 104–107 In have been investigated by using total absorption γ -ray spectrometry on mass-separated sources. The experimental Gamow–Teller strength, deduced as a function of the excitation energy in the daughter nuclei 104–107 Cd, is compared to shell-model predictions.

The β decay of the very neutron-deficient isotope 101Sn was studied at the GSI on-line mass separator using silicon detectors for recording charged particles and germanium detectors for γ-ray spectroscopy. Based on the β-delayed proton data the production cross-section of 101Sn in the 50Cr + 58Ni fusion-evaporation reaction was determined to be about 60nb. The half-life of 101Sn was measured to be 1.9(3)s. For the first time β-delayed γ-rays of 101Sn were tentatively identified, yielding weak evidence for a cascade of 352 and 1065keV transitions in 101In. The results for the 101Sn decay as well as those from previous work on the 103Sn decay are discussed by comparing them to predictions obtained from shell model calculations employing a new interaction in the 88Sr to 132Sn model space.

The usefulness of a simple numerical correction method of electronic pulse pileup distortion in measured energy spectra is investigated. The algorithm only requires the knowledge of the true pulse shape. The accuracy of the correction achieved for total absorption gamma-ray spectroscopy measurements with NaI(Tl) detectors is demonstrated.

The GT beta decay of 150 Ho has been studied with a Total Absorption Spectrometer (TAS), with an array of 6 Euroball CLUSTER Ge detectors (the CLUSTER CUBE), and with an alpha detector. The three techniques complement each other. The results provide the first observation of an extremely sharp resonance in GT beta decay.

The response of a large NaI(Tl) total absorption spectrometer for β-decay studies is investigated.The accuracy of Monte Carlo simulations taking into account the light yield non-proportionality of NaI(Tl) and the detailed geometry is assessed through comparison with spectra measured for several radioactive sources.

The β decay of 103Sn, a three-neutron-particle nucleus with respect to the 100Sn core, was investigated at the GSI on-line mass separator using an array of 17 germanium crystals and a total absorption spectrometer. A total of 31 β-delayed γ-rays (29 new) of the 103Sn →103 In decay were observed and, on the basis of β-γ-γ coincidences, the 103Sn decay scheme was established for the first time. By means of total absorption spectroscopy, β intensities, the Gamow-Teller strength distribution and the summed Gamow-Teller strength value of 3.5±0.5 were determined for this decay. Its half-life and QEC value were found to be 7.0±0.2 s and 7.64±0.7 MeV, respectively. The β-delayed proton branching ratio was measured to be 1.2±0.1%. The results are discussed in comparison with shell-model predictions based on realistic and empirical interactions.

The β-delayed proton decay of 113Xe was investigated by means of a total absorption γ-ray spectrometer and a telescope for particle detection. The energy window available for the β-delayed proton decay of 113Xe and the relative branching ratios for proton transitions to the 112Te states were remeasured. The lifetimes of proton unstable 113I states populated in the electron capture decay of 113Xe were determined by means of the particle-X-ray coincidence technique. The results of the lifetime measurements are compared with statistical-model calculations.

� SocietItaliana di Fisica / Springer-Verlag 2005 Abstract. The experimental decay properties of the (21 + ) isomer in 94 Ag are briefly discussed.

We have observed direct one-proton decay of the 21 isomer in the N Z nuclide 94Ag into highspin states in 93Pd by detecting protons in coincidence with - correlations and applying gates based on known 93Pd levels. Two decay branches have been identified, with proton energies of 0.79(3) and 1.01(3) MeV and branching ratios of 1.9(5)% and 2.2(4)%, respectively. The corresponding partial halflife values are 21(6) and 18(4) s. The Q value of the direct proton decay of the 21 isomer was found to be 5.78(3) MeV. The very small reduced widths of the observed proton decays might reflect dominating collective configurations in the 21 isomer, and the fine structure of the proton spectrum might indicate a strong deformation of this state.

The β decay of the neutron-deficient isotope 103 In was investigated by using total absorption γ-ray spectrometry on mass-separated sources. The measurement reveals a high-lying resonance of the β-decay strength in striking disagreement with high-resolution γ-ray data. The result is discussed in comparison with shell-model predictions.

The β decay of 94 Ag, a nucleus with three proton and three neutron holes with respect to 100 Sn, was investigated at the GSI on-line mass separator by using an array of germanium and silicon detectors. On the basis of a βγγ coincidence measurement, the previously reported decay scheme has been considerably improved and evidence is presented for a spin–gap isomer with a spin-parity assignment of (21 + ), i.e., the highest spin ever observed in β decay. The half-life of the low-spin isomer (7 + ) was remeasured to be 0.59(2) s, whereas the half-life of the high-spin isomer was determined as 0.47(8) s. For the states in 94 Ag and 94 Pd, large-scale shell-model calculations that include up to 4p–4h excitations across the N = Z =50 shell gap and employ a realistic interaction were carried out. These core excitations play a crucial role in generating the E 4 isomerism required for the interpretation of the long half-life of the (21 + ) state in 94 Ag.

The decay of the s7+d and s21+d isomers of the N=Z isotope 94Ag was studied at the GSI on-line mass separator by measuring b-delayed protons, g rays, proton-g and proton-g-g coincidences as well as the b-strength distribution. We have observed high-spin (up to 39/2) states in 93Rh populated by proton emission following the b decay of the 94Ag isomers. The major part of the population is related to the b decay of the known s7+d isomer whose half-life is 0.61s2d s. The assignment of the high-spin s21+d isomer in 94Ag with a half-life of 0.39s4d s has been confirmed. The excitation energy and b-decay energy of the s21+d isomer were measured to be at least 5.4 and 17.7 MeV, respectively. At this excitation energy, the s21+d isomer is expected to be unbound to direct one-proton, two-proton, or a decays. The remarkably long half-life of the s21+d isomer with the highest spin and excitation energy ever observed for b-decaying nuclei makes a new textbook example of a nuclear high-spin trap. The branching ratios for b-delayed proton emission are about 20% and 27% for the decays of the s7+d and s21+d isomers, respectively. The properties of the experimentally identified 93Rh levels are discussed in comparison to shell-model predictions.

The β-decay properties of ground-state and isomer of 103In were investigated by means of γ-ray spectroscopy. The half-lives of 103g In and 103m In were determined to be 60 ± 1 s and 34 ± 2 s, respectively. Out of 149 γ transitions ascribed to the decay of 103g In, 104 have been placed in a decay scheme including 55 excited states of 103g Cd. The main part of the resulting distribution of the Gamow-Teller strength B(GT) is associated with the feeding of 103Cd levels at excitation energies around 3 MeV. This observation can be interpreted as a sign of dominant feeding of three-quasiparticle states in 103Cd, which correspond to the 1+(πg 9/2 −1 , vg7/2)⊗πg9/2 shell-model configuration spread over many levels. The sum of the B(GT) values deduced from the present γ-ray data amounts to 0. 34, which provides a lower limit to the total Gamow-Teller strength. The B(GT) distribution for 103In decay is compared to the corresponding experimental results for 105,107,109In and to theoretical predictions for 99,101In. The latter were calculated by using an advanced spherical shell model. The β-branching ratio for the 103m In decay is estimated and compared with the relevant values for the neighbouring indium isotopes including 101In whose half-life was determined to be 14. 9 ± 1.2 s.

The β decay of 96Ag (Z=47,N=49) was investigated by measuring positrons, X rays as well as β-delayed protons and γ rays. The γ radiation was studied by means of germanium detectors and a NaI total-absorption spectrometer. Two β-decaying isomers in 96Ag were established with half-lives of 4.40(6) and 6.9(6) s and tentative spin–parity assignments of (8+) and (2+), respectively. For both isomers, the intensities of β transitions to low-lying levels of 96Pd (Z=46,N=50) and β-delayed proton decays to levels in 95Rh (Z=45,N=50) were measured. Several new 96Pd levels were firmly established. The level energies, their γ decays and the Gamow–Teller decay of 96Ag are compared to shell-model predictions. A new low-lying level in 95Rh was found at 680 keV excitation energy. Through a comparison with low-lying states of N=50 isotones, this level is interpreted as the first excited 7/2+ state built on the proton 9/2+ ground state. The assignments of further excited states in 95Rh are 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.

By using mass-separated sources, positrons as well as β-delayed protons and γ-rays were measured from the β-decay of 102 In ( T 1 2 = 22 ± 1 s ) and 100 In ( T 1 2 = 6.1 ± 0.9 s ). In particular, the average β + (β + + EC ) ratio for the decay of 102 In was measured to be 0.76(4) and the level scheme of 102 Cd was extended. Whereas no direct β + EC feeding of the identified 102 Cd levels was observed, there is evidence for population of 102 Cd states at high excitation energy followed by statistical γ-decay. This feature, which has been deduced on the basis of the measured positron spectrum and the measured β + (β + + EC ) ratio of the 102 In decay, is compared to the decay properties of the heavier odd-odd indium isotopes 104 In, 106 In and 108 In, and is also used to interpret the observed β-delayed proton data of 102 In and 100 In. For the first time, large-space shell-model calculations have been performed for the Gamow-Teller decay of heavy odd-odd nuclei. The decay results from these calculations are in good overall agreement with the gross decay properties of 102 In and 100 In deduced from the experiment.

International audience; The half-lives of fully ionized and hydrogen-like (H-like) I-122 ions have been measured in a heavy-ion storage ring. The beta(+)-decay constants for both charge states and the electron capture (EC) decay constant of H-like ions have been determined. The EC-decay constant in H-like I-122 ions lambda(H-like)(EC) = 7.35(33) . 10(-4) s(-1) is, within the uncertainty, the same as the one in neutral atoms. This result is in agreement with the estimates of recent theoretical considerations on the EC-decay of few-electron ions that explicitly take into account the conservation of the total angular momentum of the nucleus plus lepton(s) system and its projections. No firm confirmation could be concluded from our results on the predicted effect that allowed Gamow-Teller transitions become forbidden if the initial and final total angular momenta are not equal.

We propose to install a storage ring at an ISOL-type radioactive beam facility for the first time. Specifically, we intend to setup the heavy-ion, low-energy ring TSR at the HIE-ISOLDE facility in CERN, Geneva. Such a facility will provide a capability for experiments with stored secondary beams that is unique in the world. The envisaged physics programme is rich and varied, spanning from investigations of nuclear ground-state properties and reaction studies of astrophysical relevance, to investigations with highly-charged ions and pure isomeric beams. The TSR might also be employed for removal of isobaric contaminants from stored ion beams and for systematic studies within the neutrino beam programme. In addition to experiments performed using beams recirculating within the ring, cooled beams can also be extracted and exploited by external spectrometers for high-precision measurements. The existing TSR, which is presently in operation at the Max-Planck Institute for Nuclear Physics in Heidelberg, is well-suited and can be employed for this purpose. The physics cases as well as technical details of the existing ring facility and of the beam and infrastructure requirements at HIE-ISOLDE are discussed in the present technical design report. ispartof: European Physical Journal. Special Topics vol:207 issue:1 pages:1-117 status: published

This article reviews the decay studies of neutron-deficient nuclei within the mass region \ensuremathA=56--100 performed at the Ion-Guide Isotope Separator On-Line (IGISOL) facility in the University of Jyväskylä over last 25 years. Development from He-jet measurements to on-line mass spectrometry, and eventually to atomic mass measurements and post-trap spectroscopy at IGISOL, has yielded studies of around 100 neutron-deficient nuclei over the years. The studies form a solid foundation to astrophysical rp -process path modelling. The focus is on isomers studied either via spectroscopy or via Penning-trap mass measurements. The review is complemented with recent results on the ground and isomeric states of 90Tc . The excitation energy of the low-spin isomer in 90Tc has been measured as \ensuremathEx=144.1(17) keV with JYFLTRAP double Penning trap and the ground state of 90Tc has been confirmed to be the (8+) state with a half-life of \ensuremathT1/2=49.2(4) s. Finally, the mass-excess results for the spin-gap isomers 53Co m and 95Pd m and implications from the JYFLTRAP mass measurements for the (21+) isomer in 94Ag are discussed. peerReviewed

The beta decays of ^{150}Er, ^{152}Yb, and ^{156}Yb nuclei are investigated using the total absorption spectroscopy technique. These nuclei can be considered possible candidates for forming the beam of a monoenergetic neutrino beam facility based on the electron capture (EC) decay of radioactive nuclei. Our measurements confirm that for the cases studied, the EC decay proceeds mainly to a single state in the daughter nucleus.

The study of beta‐delayed proton emission is a well known method to aid the determination of the beta strength distribution in nuclei far from the stability line. At the neutron deficient side of the nuclear chart the process of proton or alpha emission from excited states is energetically allowed when one goes far enough from stability. However, beta‐delayed alphas have seldom been measured for nuclei heavier than A = 20. Here we present a study of the beta‐delayed alpha‐particle emission from 152Tm and 150Ho and their importance in the full B(GT) distribution. © 2011 American Institute of Physics

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.

An application of the totalγ-absorption (TGA) spectroscopy to measurements of theβ-decay energies (Q) for nuclei far from stability is described. This approach provides theQ-values with accuracies up to 60 keV. TheQ values determined by this method at the IRIS facility for 64 nuclides in the mass region fromA=76 toA=165 are presented.

The β decay of 58Cu has been studied by means of total absorption γ-ray spectroscopy. The β feeding to the 58Ni states has been measured, and the strength of the 58Cu(1+) →58Ni(0+) Gamow-Teller transition has been determined with improved accuracy.