Department of Physics

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IGISOL

The exotic nuclei and beams group studies properties of nuclei employing Penning-trap mass spectrometry as well as laser and decay spectroscopy at the IGISOL-4 facility.

Contact persons: , and

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JYFLTRAP - A part of IGISOL system.

The exotic nuclei and beams group, aka the IGISOL group is a part of the Center of Excellence (CoE) of the Academy of Finland.  We are performing our studies locally at the Jyväskylä Ion Guide Isotope Separator On-Line (IGISOL) facility, as well as at a number of other laboratories such as the ISOLDE facility in CERN, at GANIL and in Helmholzzentrum GSI, the location of the future radioactive beam facility FAIR. We are also actively involved in work to support the development of international future facilities EURISOL and aforementioned FAIR, which we have done in close collaboration with HIP, the Helsinki Institute of Physics.  An important form of our international collaboration is also participation in research networks.

The research at the IGISOL facility in Jyväskylä since early 1980's until 2010 has recently been pictured in a laboratory portrait: "Three decades of research at IGISOL", whose articles are published in special issues of European Physical Journal A and Hyperfine Interactions.


  • Technical developments
    • Laser developments 2015 »


      A new setup to perform saturated absorption spectroscopy has been developed and used in connection with a rubidium-filled reference cell. This allows for Doppler-free spectroscopy with a resolution limited only by the power-broadened linewidth of the atomic transition. By measuring the well-known hyperfine structure of the D1 line of rubidium, the free spectral range of two Fabry-Pérot Interferometers has been measured.

      In 2015 the “nuClock” consortium received notification from the EU that the application to the Future and Emerging Technologies (FET-OPEN) call in Horizon 2020 was successful. With a goal of developing a nuclear clock based on a unique low-energy nuclear transition in 229Th, the first objective is to find clear evidence of the transition. As a partner in the consortium, we have hired Sarina Geldhof to work as a PhD student on the project. The first 232Th samples for testing at IGISOL arrived from Vienna in December.

    • Developments for neutron-induced fission 2015 »


      Some fission yield measurements and theoretical calculations propose that fast neutron-induced fission of natural uranium would be beneficial over proton-induced fission, normally utilised at the IGISOL facility to produce very neutron rich nuclei. Switching to neutrons is not straightforward, mostly because a vast amount of intensity is lost in the conversion of the proton beam into neutrons. 

      A prototype of a beryllium-based neutron converter has been constructed and the neutron production characterised. The neutron field was found to be in accordance with simulations. In 2015, the first tests with a neutron-induced fission ion guide took place.

      The work has been performed in collaboration with Uppsala University. In particular, the simulations of the ion stopping and the neutron production made by Uppsala colleagues have been most useful in this project.

  • Recent research
    • I-187  Collinear laser spectroscopy of long-lived Pu isotopes »
    • I-199: Quantum-state selective decay spectroscopy: Proton decay branch of 53Com »
    • I-207: Single and double beta decay Q-value of 96Zr »


      The neutrinoless double beta (0νββ) decay is currently of significant interest in nuclear and particle physics. An observation of this decay mode not only gives insight into the nature of the neutrino but also provides information about its absolute mass scale. The critical quantity which enters in theoretical model calculations is the nuclear matrix element [1]. It describes the underlying nuclear physics, and because of its complexity, neither the matrix elements nor the adequacy of the models can be easily assessed.

      We measured the single and double beta decay Q-value of 96Zr. This nucleus has the third largest ββ Q-value, topped only by 48Ca and 150Nd. Furthermore, it is also one of the two nuclides (the other is 48Ca) unstable against single β-decay. If single β-decay is observed in either of these systems, matrix element calculations can be directly tested for double beta decay. Presently, the matrix element is only theoretically determined. Its value has been calculated within the framework of the QRPA model by J. Suhonen’s group.

      Just prior to our work, the 96Zr double beta decay Q-value was measured with Michigan State University's LEBIT trap to be nearly 7 keV higher [2] than in the most recent atomic mass evaluation (AME2012 [3]). Whether this discrepancy would be manifest also in the single beta decay Q-value was still to be confirmed. The measurement imposed an experimental challenge since 96Zr and96Nb are separated by only about 1.8 parts per million in mass. Although challenging, the two were separated with the in-house developed Ramsey cleaning method [4].

      No discrepancy in the single β-decay Q-value was found. The precision of the value was, nevertheless, improved by 20-fold. The 7 keV discrepancy found by the LEBIT group in the ββ Q-value was confirmed.

      This project was done in collaboration with the University of Münster, Calgary, Bratislava and with JYFL J. Suhonen's theory group.

      [1] J. Shone, et al., J. Phys. G: Nucl. Part. Phys. 39 (2012) 124005, doi:10.1088/0954-3899/39/12/124005
      [2] K. Gulyuz, et al., Phys. Rev. C 91, 055501 (2015), doi:10.1103/PhysRevC.91.055501
      [3]  G. Audi, et al. , Chinese physics C 36(12) 1157 (2012).
      [4] T. Eronen, et al., Nuclear Instr. and Methods B 266 (2008) 4527–4531, doi:10.1016/j.nimb.2008.05.076.

    • I-200: The first Penning-trap mass measurement of the TZ=-3/2 nucleus 31Cl »
  • Recent publications
    • 17/2017. C. Magron, et al.: Precise measurements of half-lives and branching ratios for the β decay of two mirror nuclei, 23Mg and 27Si European Physical Journal A 53: 77 (2017) - DOI: 10.1140/epja/i2017-12271-0 - Submitted on 4 December 2016, accepted 4 April 2017, published 24 April 2017
      Authors C. Magron, A. Alfaurt, B. Blank, L. Daudin, T. Eronen, M. Gerbaux, J. Giovinazzo, D. Gorelov, H. Guérin, J. Hakala, V. Kolhinen, J. Koponen, T. Kurtukian Nieto, I. Moore, H. Penttilä, I. Pohjalainen, J. Reinikainen, M. Reponen, S. Rinta-Antila, M. Roche, A. de Roubin, N. Smirnova, B. Thomas, A. Voss, and L. Xayavong
      Abstract Half-lives and branching ratios for the two mirror β decays of 23Mg and 27Si have been measured at the University of Jyvaskyla with the IGISOL facility. The results obtained, T1/2 = 11.303(3) s and T1/2 = 4.112(2) s for the half-lives of 23Mg and 27Si, respectively, are 7 and 9 times more precise than the averages of previous measurements. The values obtained for the superallowed branching ratios of 23Mg and 27Si are B.R. = 92.18(8)% and B.R. = 99.79(3)%, respectively. The result for 23Mg is three times more precise than the average of the previous measurements, while for 27Si the precision has not been improved, the average of the previous measurements being already very precise. Isospin breaking corrections have been calculated for the two nuclei to determine the corrected Ft value.
      Acknowledgements The authors would like to acknowledge the continuous effort of the whole Jyvaskyla accelerator laboratory staff for ensuring a smooth running of the experiment. This work was supported by the Academy of Finland under the Finnish Centre of Excellence Programme 2012-2017 (Project No. 213503, Nuclear and Accelerator-Based Physics Research at JYFL), by the Conseil Régional d’Aquitaine, and by the European Community FP7 - Capacities - Integrated Infrastructure Initiative - contract ENSAR nO 262010. by the European Union 7th Framework Programme ”Integrated Infrastructure Initiative - Transnational Access”, ENSAR.
    • 16/2017. A. Voss, et al.: High-resolution laser spectroscopy of long-lived plutonium isotopes Physical Review A 95, 032506 (2017) - DOI: 10.1103/PhysRevA.95.032506 - Submitted on 8 December 2016, published 24 March 2017
      Authors A. Voss, V. Sonnenschein, P. Campbell, B. Cheal, T. Kron, I.D. Moore, I. Pohjalainen, S. Raeder, N. Trautmann, K. Wendt
      Abstract Long-lived isotopes of plutonium were studied using two complementary techniques, high-resolution resonance ionisation spectroscopy (HR-RIS) and collinear laser spectroscopy (CLS). Isotope shifts have been measured on the 5f6 7s2 7F0 → 5f5 6d2 7s (J=1) and 5f6 7s2 7F1 → 5f6 7s 7p (J=2) atomic transitions using the HR-RIS method and the hyperfine factors have been extracted for the odd mass nuclei 239,241Pu. Collinear laser spectroscopy was performed on the 5f6 7s 8F 1/2 →J=1/2(27523.61cm−1 ) ionic transition with the hyperfine A factors measured for 239Pu. Changes in mean-squared charge radii have been extracted and show a good agreement with previous non-optical methods, with an uncertainty improvement by approximately one order of magnitude. Plutonium represents the heaviest element studied to date using collinear laser spectroscopy.
      Acknowledgements We thank P. Thörle-Pospiech and J. Runke for preparing the Pu filaments. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 654002, the Academy of Finland under the Finnish Centre of Excellence Programme 2012–2017 (Project No. 251353, Nuclear and Accelerator-Based Physics Research at Jyfl), the Sciences and Technology Facilities Council (Stfc) of the United Kingdom, the Fwo-Vlaanderen (Belgium), Goa/2010/010 (Bof KU Leuven), the Iap Belgian Science Policy (BriX network P7/12) and a Grant from the European Research Council (Erc-2011-Adg-291561-Helios).
    • 15/2017. D. A. Nesterenko, et al.: High-precision mass measurements for the isobaric multiplet mass equation at A = 52 Journal of Physics G: Nuclear and Particle Physics 44 065103 (2017) - DOI: 10.1088/1361-6471/aa67ae - Accepted 20 March 2017, Published 19 April 2017, Available online 20 March 2017
      Authors D.A. Nesterenko, A. Kankainen, L. Canete, M. Block, D. Cox, T. Eronen, C. Fahlander, U. Forsberg, J. Gerl, P. Golubev, J. Hakala, A. Jokinen, V.S. Kolhinen, J. Koponen, N. Lalovic, Ch. Lorenz, I.D. Moore, P. Papadakis, J. Reinikainen, S. Rinta-Antila, D. Rudolph, L.G. Sarmiento, A. Voss, and J. Äystö
      Abstract Masses of 52Co, 52Com, 52Fe, 52Fem, and 52Mn have been measured with the JYFLTRAP double Penning trap mass spectrometer. Of these, 52Co and 52Com have been experimentally determined for the first time and found to be more bound than predicted by extrapolations. The isobaric multiplet mass equation for the T = 2 quintet at A = 52 has been studied employing the new mass values. No significant breakdown (beyond the 3σ level) of the quadratic form of the IMME was observed (χ2/n = 2.4). The cubic coefficient was 6.0(32) keV (χ2/n = 1.1). The excitation energies for the isomer and the T = 2 isobaric analogue state in 52Co have been determined to be 374(13) keV and 2922(13) keV, respectively. The Q value for the proton decay from the 19/2 isomer in 53Co has been determined with an unprecedented precision, Qp = 1558.8(17) keV. The proton separation energies of 52Co and 53Ni relevant for the astrophysical rapid proton capture process have been experimentally determined for the first time.
      Acknowledgements This work has been supported by the Academy of Finland under the Finnish Centre of Excellence Programme 2012 - 2017 (Nuclear and Accelerator Based Physics Research at JYFL) and the Swedish Research Council (VR 2013-4271). A.K., D.N., and L.C. acknowledge support from the Academy of Finland under grant No. 275389.
    • 14/2017. P. V. Bilous, et al.: Internal conversion from excited electronic states of 229Th ions > Editor's Suggestion Physical Review A 95, 032503 (2017) - DOI: 10.1103/PhysRevA.95.032503 Submitted on 22 December 2016, published 13 March 2017
      Authors Pavlo V. Bilous, Georgy A. Kazakov, Iain D. Moore, Thorsten Schumm, and Adriana Palffy
      Abstract The process of internal conversion from excited electronic states is investigated theoretically for the case of the vacuum-ultraviolet nuclear transition of 229Th. Due to the very low transition energy, the 229Th nucleus offers the unique possibility to open the otherwise forbidden internal conversion nuclear decay channel for thorium ions via optical laser excitation of the electronic shell. We show that this feature can be exploited to investigate the isomeric state properties via observation of internal conversion from excited electronic configurations of Th+ and Th2+ ions. A possible experimental realization of the proposed scenario at the nuclear laser spectroscopy facility IGISOL in Jyväskylä, Finland is discussed.
      Acknowledgements The authors gratefully acknowledge funding by the EU FET-Open project 664732.
    • 13/2017. R. P. Groote, et al.: Efficient, high-resolution laser ionization spectroscopy using weak transitions to long-lived excited states Physical Review A 95, 032502 (2017) - DOI: 10.1103/PhysRevA.95.032502 Submitted on 2 December 2016, published 7 March 2017
      Authors R. P. de Groote, M. Verlinde, V. Sonnenschein, K. T. Flanagan, I. Moore, and G. Neyens
      Abstract Laser spectroscopic studies on minute samples of exotic radioactive nuclei require very efficient experimental techniques. In addition, high resolving powers are required to allow extraction of nuclear structure information. Here we demonstrate that by using weak atomic transitions, resonance laser ionization spectroscopy is achieved with the required high efficiency (1%–10%) and precision (linewidths of tens of MHz). We illustrate experimentally and through the use of simulations how the narrow experimental linewidths are achieved and how distorted resonance ionization spectroscopy line shapes can be avoided. The role of the delay of the ionization laser pulse with respect to the excitation laser pulse is crucial: the use of a delayed ionization step permits the best resolving powers and line shapes. A high efficiency is maintained if the intermediate level has a lifetime that is at least of the order of the excitation laser pulse width. A model that describes this process reproduces well the observed features and will help to optimize the conditions for future experiments. The simulation code is available upon request to the authors.
      Acknowledgements We acknowledge the support of the ISOLDE collaboration and technical teams. We are grateful to the COLLAPS collaboration for the use of their cw Ti:sapphire laser system and WaveTrain doubling unit. We thank W. Gins for fruitful discussions and for comparisons to simulations with rate equation codes. Thisworkwas supported by the BriX Research Program No. P7/12 and FWO-Vlaanderen (Belgium) and GOA 15/010 from KU Leuven, ERC Consolidator Grant No. 648381, the Science and Technology Facilities Council Consolidated Grant No. ST/F012071/1 and Continuation Grant No. ST/J000159/1, and the EU Seventh Framework through ENSAR (506065). K.T.F. was supported by STFC Advanced Fellowship Scheme Grant No. ST/G006415/1. This work was also supported by the Academy of Finland under the Center of Excellence Programme 2012–2017 (Nuclear and Accelerator Based Physics Research at JYFL).
    • 12/2017. Oliver S. Kirsebom, et al.: Towards an experimental determination of the transition strength between the ground states of 20F and 20Ne Japanese Physical Society Conference Proceedings 14, 021008 (2017) - DOI: 10.7566/JPSCP.14.021008 Submitted on 19 August 2016, published 28 February 2017
      Authors Oliver S. Kirsebom, Joakim Cederkäll, David G. Jenkins, Pankaj Joshi, Rauno Julin, Anu Kankainen, Tibor Kibédi, Olof Tengblad, and Wladyslaw H. Trzaska
      Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)
      Abstract Electron capture on 20Ne is thought to play a crucial role in the final evolution of electron-degenerate ONe stellar cores. Recent calculations suggest that the capture process is dominated by the second-forbidden transition between the ground states of 20Ne and 20F, making an experimental determination of this transition strength highly desirable. To accomplish this task we are refurbishing an intermediate-image magnetic spectrometer capable of focusing 7 MeV electrons, and designing a scintillator detector surrounded by an active cosmic-ray veto shield, which will serve as an energy-dispersive device at the focal plane.
    • 11/2017. Anu Kankainen, et al.: Mass measurements for the rp process Japanese Physical Society Conference Proceedings 14, 011002(2017) - DOI: 10.7566/JPSCP.14.011002Submitted on 18 August 2016, published 28 February 2017
      Authors Anu Kankainen, Laetitia Canete, Tommi Eronen, Dmitry Gorelov, Jani Hakala, Ari Jokinen, Veli S. Kolhinen, Jukka Koponen, Iain D. Moore, Dimitrii Nesterenko, Juuso Reinikainen, Sami Rinta-Antila, and Juha Äystö
      Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)
      Abstract One of the key parameters for the reaction network calculations for the rapid proton capture (rp) process, occurring e.g., in type I X-ray bursts, are the masses of the involved nuclei. Nowadays, masses of even rather exotic nuclei can be measured very precisely employing Penning-trap mass spectrometry. With the JYFLTRAP Penning trap at the IGISOL facility, masses of around 100 neutron-deficient nuclei have been determined with a typical precision of a few keV. Most recently, 25Al, 30P, 31Cl and 52Co have been measured. Of these, the precision of the mass-excess value of , 31Cl was improved from 50 to 3.4 keV, and the mass of 52Co was experimentally determined for the first time. The mass of 31Cl is relevant for estimating the waiting-point conditions for , 30S as the 31Cl 30S–30S(p, γ)31Cl equilibrium ratio depends exponentially on the Q value. For 52Co , located at the path towards 56Ni, a deviation from the extrapolated mass value has been revealed. In this contribution, recent JYFLTRAP experiments for the rp process will be discussed.
      Acknowledgements This work has been supported by the Academy of Finland under the Finnish Centre of Excellence Programme 20122017 (Nuclear and Accelerator Based Physics Research at JYFL). A.K., D.N., and L.C. acknowledge support from the Academy of Finland under grant No. 275389.
    • 10/2017. J.L. Tain, et al.: r process (n,γ) rate constrainsts from the γ-emission of neutron unbound states in β decay Japanese Physical Society Conference Proceedings 14, 010607 (2017) - DOI: 10.7566/JPSCP.14.010607 Submitted on 10 September 2016, published 28 February 2017
      Authors J. L. Tain, V. Guadilla, E. Valencia, A. Algora, A.-A. Zakari-Issoufou, S. Rice, J. Agramunt, J. Äystö, L. Batist, M. Bowry, J. A. Briz, V. M. Bui, R. Caballero-Folch, D. Cano-Ott, A. Cucoanes, V.-V. Elomaa, T. Eronen, E. Estevez, M. Estienne, M. Fallot, G. F. Farrelly, L. M. Fraile, E. Ganioglu, A. R. Garcia, W. Gelletly, B. Gomez-Hornillos, D. Gorelov, V. Gorlychev, J. Hakala, A. Jokinen, M. D. Jordan, A. Kankainen, V. S. Kolhinen, F. G. Kondev, J. Koponen, M. Lebois, T. Mart´ınez, P. Mason, E. Mendoza, M. Monserrate, A. Montaner-Piz´ a, I. Moore, E. Nacher, S. Orrigo, H. Penttilä, Zs. Podoly´ak, I. Pohjalainen, A. Porta, P. Regan, J. Reinikainen, M. Reponen, S. Rinta-Antila, J. Rissanen, B. Rubio, K. Rytkönen, T. Shiba, V. Sonnenschein, A. A. Sonzogni, V. Vedia, A. Voss, J.N. Wilson
      Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)
      Abstract 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 sectionforhighlyunstableneutron-richnucleicanbededuced.Asurprisinglylarge γ branchingwas 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 with impact on r process abundance calculations.
    • 9/2017. Laetitia Canete et al.: High-Precision Proton-Capture Q Values for 25Al(p, γ)26Si and 30P(p, γ)31 Japanese Physical Society Conference Proceedings 14, 020503 (2017) - DOI: 10.7566/JPSCP.14.020503 Submitted on 16 August 2016, published 28 February 2017
      Authors Laetitia Canete, Anu Kankainen, Tommi Eronen, Dmitry Gorelov, Jani Hakala, Ari Jokinen, Veli Kolhinen, Jukka Koponen, Iain D. Moore, Juuso Reinikainen, and Sami Rinta-Antila
      Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)
      Abstract The masses of astrophysically relevant nuclei, 25Al and 30P, have recently been measured with the JYFLTRAP double Penning trap at the new IGISOL-4 facility at the University of Jyväskylä. Unparalleled precisions of 63 and 64 eV were achieved for the 25Al and 30P masses, respectively. The proton-capture Q values for 25Al(p, γ)26Si and 30P(p, γ)31S were also determined, and their precisions improved by a factor of 4 and 2, respectively, in comparison with AME12. The impact of the more precise values on the resonant proton-capture rate has also been studied.
      Acknowledgements This work has been supported by the EU 7th framework programme Integrating Activities - Transnational Access, project number: 262010 (ENSAR) and by the Academy of Finland under the Finnish Centre of Excellence Programme 2012-2017 (Nuclear and Accelerator Based Physics Research at JYFL). The authors acknowledge the support from the Academy of Finland under project No. 275389.
    • 8/2017. A. Kankainen, et al.: Measurement of key resonance states for the 30P(p, γ)31S reaction rate, and the production of intermediate-mass elements in nova explosions Physics Letters B (2017). - DOI: 10.1016/j.physletb.2017.01.084 Submitted 26 August 2016, accepted 14 January 2017, available online 17 February 2017
      Authors A. Kankainen, P.J. Woods, H. Schatz, T. Poxon-Pearson, D. Doherty, V. Bader, T. Baugher, D. Bazin, B.A. Brown, J. Browne, A. Estrade, A. Gade, J. José, A. Kontos, C. Langer, G. Lotay, Z. Meisel, F. Montes, S. Noji, F. Nunes, G. Perdikakis, J. Pereira, F. Recchia, T. Redpath, M. Scott, D. Seweryniak, J. Stevens, R. Stroberg, D. Weisshaar, K. Wimmer, and R. Zegers
      Abstract We report the first experimental constraints on spectroscopic factors and strengths of key resonances in the 30P(p, γ)31S reaction critical for determining the production of intermediate-mass elements up to Ca in nova ejecta. The 30P(p, γ)31S 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 indicate the dominance of a single 3/2 resonance state at 196 keV in the region of nova burning T≈0.10–0.17GK, well within the region of interest for nova nucleosynthesis. Hydrodynamic simulations of nova explosions have been performed to demonstrate the effect on the composition of nova ejecta.
      Acknowledgements The Edinburgh group is grateful for the support from the STFC grants. A.K. acknowledges the support from the Academy of Finland under project No. 275389. J.J. acknowledges sup-port from the Spanish MINECO grant AYA2014-59084-P, the E.U. FEDER funds, and from the AGAUR/Generalitat de Catalunya grant SGR0038/2014. This work was supported by the National Science Foundation under Grants No. PHY-1403906, PHY-1430152 (JINA Center for the Evolution of the Elements) and PHY-1404442, in part by the National Nuclear Security Administration under the Stewardship Science Academic Alliance program through the DOE cooperative agreement DE-FG52-08NA28552, and by the US DOE, Office of Science, Office of Nuclear Physics, under contract number DE-AC02-06CH11357 (ANL). GRETINA was funded by the US DOE Office of Science. Operation of the array at NSCL is supported by the NSF under Cooperative Agreement PHY-1102511(NSCL) and by the DOE under Grant No. DE-AC02-05CH11231(LBNL). We thank L. Riley for providing us the UCGretina GEANT4 code.
    • 7/2017. V. Guadilla, et al.: Characterization of a cylindrical plastic β-detector with Monte Carlo simulations of optical photons =""> Nucl. Instrum. and Methods A 854 (2017) 134 –138 - DOI: 10.1016/j.nima.2017.02.047 Submitted on 14 November 2016 , accepted 14 February 2017, published online 16 February 2017
      Authors V. Guadilla, A. Algora, J. L. Tain, J. Agramunt, J. Äystö J. A. Briz, A. Cucoanes, T. Eronen, M. Estienne, M. Fallot, L. M. Fraile, E. Ganioglu, W. Gelletly, D. Gorelov, J. Hakala, A.Jokinen, D. Jordan, A.Kankainen, V. Kolhinen, J. Koponen, M. Lebois, T. Martinez, M.Monserrate, A. Montaner-Piza, I. Moore, E.Nacher, S. Orrigo, H. Penttilä, I. Pohjalainen, A.Porta, J. Reinikainen, M. Reponen, S. Rinta-Antila, B. Rubio, K. Rytkönen, T. Shiba, V. Sonnenschein, A. A. Sonzogni, E. Valencia, V. Vedia, A. Voss, J. N. Wilson, A. -A. Zakari-Issoufou
      Abstract In this work we report on the Monte Carlo study performed to reproduce experimental measurements of a new plastic-detector with cylindrical geometry. Since energy deposition simulations differ from the experimental measurements for such a complex geometry, we show how the simulation of production and transport of optical photons does allow one to obtain the shapes of the experimental spectra. Moreover, taking into account the computational effort associated with this kind of simulation, we develop a method to convert the simulations of energy deposited into light collected, depending only on the interaction point in the detector. This method represents a useful solution when extensive simulations have to be done, as in the case of the calculation of the response function in a total absorption gamma-ray spectroscopy analysis.
      Acknowledgements This work has been supported by the Spanish Ministerio de Economıa y Competitividad under the FPA2011-24553, the AIC-A-2011-0696, the FPA2014-52823-C2-1-P and the SEV-20140398 Grants, by the European Commission under the FP7/EURATOM contract 605203, and by the Spanish Ministerio de Educacion under the FPU12/01527 Grant. Helpful discussions with P. Schotanus (Scionix) and the development of the detector by Scionix are also acknowledged.
    • 6/2017. S. Kelly, et al.: Laser spectroscopy with an electrostatic ConeTrap Hyperfine Interact (2017) 238:42 - DOI: 10.1007/s10751-017-1412-z Published 23 February 2017
      Authors S. Kelly, P. Campbell, B. Cheal, T. Eronen, S. Geldhof, A. Jokinen, I. D. Moore, H. Penttilä , I. Pohjalainen, S. Rinta-Antila, V. Sonnenschein, A. Voss
      Abstract A compact electrostatic trap has been designed and installed as part of the recent upgrades to the IGISOL IV facility. The ConeTrap provides an in vacuo optical pumping site for low energy (800 eV) ionic ensembles available for interaction periods of 10-100 ms. At present, 6.7(3) % of injected mass A=98 ions can be trapped, stored for 5 ms, extracted and transported to a laser-ion interaction region. This fraction represents those ions for which no perturbation to total energy or energy spread is observed. Proposed enhancements to the trap are designed to improve the trapping efficiency by up to a factor of 5. Differential pumping and reduction in background pressure below the present 10−6 mbar will extend storage times beyond 100 ms.
    • 5/2017. R. Ferrer, et al.: Resonance ionisation in a supersonic gas jet: towards high-resolution laser spectroscopy of the heaviest elements Nature Commun. 8 (2017) 14520 - DOI: 10.1038/ncomms14520 Submitted on 25 August 2016 , accepted 9 January 2017, published 22 February 2017
      Authors R. Ferrer, A. Barzakh, B. Bastin, R. Beerwerth, M. Block, P. Creemers, H. Grawe, R. de Groote, P. Delahaye, X. Fléchard, S. Franchoo, S. Fritzsche, L. P. Gaffney, L. Ghys, W. Gins, C. Granados, R. Heinke, L. Hijazi, M. Huyse, T. Kron, Yu. Kudryavtsev, M. Laatiaoui, N. Lecesne, M. Loiselet, F. Lutton, I. D. Moore, Y. Martínez, E. Mogilevskiy, P. Naubereit, J. Piot, S. Raeder, S. Rothe, H. Savajols, S. Sels, V. Sonnenschein, J-C Thomas, E. Traykov, C. Van Beveren, P. Van den Bergh, P. Van Duppen, K. Wendt, A. Zadvornaya
      Abstract Resonant laser ionization and spectroscopy are widely used techniques at radioactive ion beam facilities to produce pure beams of exotic nuclei and measure the shape, size, spin and electromagnetic multipole moments of these nuclei. However, in such measurements it is difficult to combine a high efficiency with a high spectral resolution. Here we demonstrate the on-line application of atomic laser ionization spectroscopy in a supersonic gas jet, a technique suited for high-precision studies of the ground- and isomeric-state properties of nuclei located at the extremes of stability. The technique is characterized in a measurement on actinium isotopes around the N=126 neutron shell closure. A significant improvement in the spectral resolution by more than one order of magnitude is achieved in these experiments without loss in efficiency.
    • 4/2017. M. Czerwiński, et al.: Penning-trap-assisted study of excitations in 88Br populated in β decay of 88Se Phys. Rev. C 95, 024321 - DOI: 10.1103/PhysRevC.95.024321 - Submitted on 16 September 2016 , published 22 February 2017
      Authors M. Czerwiński, K. Sieja, T. Rząca-Urban, W. Urban, A. Płochocki, J. Kurpeta, J. Wiśniewski, H. Penttilä, A. Jokinen, S. Rinta-Antila, L. Canete, T. Eronen, J. Hakala, A. Kankainen, V. S. Kolhinen, J. Koponen, I. D. Moore, I. Pohjalainen, J. Reinikainen, V. Simutkin, A. Voss, I. Murray, and C. Nobs
      Abstract Excited levels of 88Br populated in the β decay of 88Se have been studied by means of βγ and γγ 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 Jyväskylä. The level scheme of 88Br has been constructed and logft 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, πp3/2−1(νd5/2)3, πf5/2−1(νd5/2)3, and πg9/2νg7/2 multiplets. The shell-model calculations performed in this work reproduce well the experimental results.
      Acknowledgements This work has been supported by the Polish National Science Centre under Contracts No. DEC-2013/09/B/ST2/03485 and No. DEC-2015/16/T/ST2/00340, and by the Academy of Finland under the Finnish Centre of Excellence Programme 2012-2017 (Project No. 251353, Nuclear and Accelerator-Based Physics Research at JYFL).
    • 3/2017. E. Valencia, et al.: Total Absorption γ-Ray Spectroscopy of 87Br, 88Br and 94Rb β-Delayed Neutron Emitters Phys. Rev. C 95, 024320 - DOI: 10.1103/PhysRevC.95.024320 - Submitted on 16 September 2016 , published 21 February 2017
      Authors E. Valencia, J. L. Tain, A. Algora, J. Agramunt, E. Estevez, M.D. Jordan, B. Rubio , S. Rice, P. Regan, W. Gelletly, Z. Podoly´ak, M. Bowry, P. Mason, G. F. Farrelly , A. Zakari-Issoufou, M. Fallot, A. Porta, V. M. Bui, J. Rissanen, T. Eronen, I. Moore, H. Penttilä, J. Äystö, V.-V. Elomaa, J. Hakala, A. Jokinen, V. S. Kolhinen, M. Reponen, V. Sonnenschein , D. Cano-Ott, A. R. Garcia, T. Mart´ınez, E. Mendoza , R. Caballero-Folch, B. Gomez-Hornillos, V. Gorlichev, F. G. Kondev , A. A. Sonzogni, L. Batist
      Abstract 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 shows 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 to explain the large value for bromine isotopes as due to nuclear structure. However the branching for 94Rb although much smaller hints to the need of increasing the radiative width Γγ by one order of magnitude. This leads 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.
      Acknowledgements This work was supported by Spanish Ministerio de Econom´ıa y Competitividad under grants FPA2008-06419, FPA2010-17142, FPA2011- 24553, FPA2014-52823-C2-1P,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. 251353, Nuclear and Accelerator-Based Physics Research at JYFL). Work supported by EPSRC( UK) and STFC(UK). Work partially supported by the European Commission under the FP7/EURATOM contract 605203. We thank D. Lhuillier for making available in digital form data tabulated in Ref. [60].
    • 2/2017. T. Eronen, et al.: QECvalue of the Superallowed β-Emitter 42Sc Phys. Rev. C 95, 025501 - DOI: 10.1103/PhysRevC.95.025501 - Submitted on 23 November 2016 , published 10 February 2017
      Authors T. Eronen, J.C. Hardy, L. Canete, A. Jokinen, J. Hakala, A. Kankainen, V. S. Kolhinen, J. Koponen, I.D. Moore, I.M. Murray, H. Penttilä, I. Pohjalainen, O. Poleshchuk, J. Reinikainen, S. Rinta-Antila, N. Soukouti, A. Voss, and J. Äystö
      Abstract The QEC value of the superallowed β+-emitter 42Sc has been measured with the JYFLTRAP Penning-trap mass spectrometer at the University of Jyväskylä to be 6426.350(53) keV. This result is at least a factor of four more precise than all previous measurements, which were also inconsistent with one another. As a byproduct we determine the excitation energy of the 7+-isomeric state in 42Sc to be 616.762(46) keV, which deviates by 8 sigma from the previous measurement.
      Acknowledgements This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Award Number DE-FG03- 93ER40773, by the Welch Foundation under Grant No.A-1397, and by the Academy of Finland under the Finnish Centre of Excellence Programme 2012-2017 (Nuclear and Accelerator Based Physics Research at JYFL). A.K. and L.C. acknowledge the support from the Academy of Finland under project No. 275389.
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