A. Di Nitto

Synthesis and detection of a seaborgium carbonyl complex

A carbonyl compound that tips the scales Life is short for the heaviest elements. They emerge from high-energy nuclear collisions with scant time for detection before they break up into lighter atoms. Even et al. report that even a few seconds is long enough for carbon to bond to the 106th element, seaborgium (see the Perspective by Loveland). The authors used a custom apparatus to direct the freshly made atoms out of the hot collision environment and through a stream of carbon monoxide and helium. They compared the detected products with theoretical modeling results and conclude that hexacarbonyl Sg(CO)6 was the most likely structural formula. Science, this issue p. 1491; see also p. 1451 A special apparatus enables synthesis of a compound with carbon bonds to a short-lived element produced via nuclear reaction. [Also see Perspective by Loveland] Experimental investigations of transactinoide elements provide benchmark results for chemical theory and probe the predictive power of trends in the periodic table. So far, in gas-phase chemical reactions, simple inorganic compounds with the transactinoide in its highest oxidation state have been synthesized. Single-atom production rates, short half-lives, and harsh experimental conditions limited the number of experimentally accessible compounds. We applied a gas-phase carbonylation technique previously tested on short-lived molybdenum (Mo) and tungsten (W) isotopes to the preparation of a carbonyl complex of seaborgium, the 106th element. The volatile seaborgium complex showed the same volatility and reactivity with a silicon dioxide surface as those of the hexacarbonyl complexes of the lighter homologs Mo and W. Comparison of the product’s adsorption enthalpy with theoretical predictions and data for the lighter congeners supported a Sg(CO)6 formulation.

Decomposition studies of group 6 hexacarbonyl complexes. Part 1: Production and decomposition of Mo(CO)6 and W(CO)6

Abstract Chemical studies of superheavy elements require fast and efficient techniques, due to short half-lives and low production rates of the investigated nuclides. Here, we advocate for using a tubular flow reactor for assessing the thermal stability of the Sg carbonyl complex – Sg(CO)6. The experimental setup was tested with Mo and W carbonyl complexes, as their properties are established and supported by theoretical predictions. The suggested approach proved to be effective in discriminating between the thermal stabilities of Mo(CO)6 and W(CO)6. Therefore, an experimental verification of the predicted Sg–CO bond dissociation energy seems to be feasible by applying this technique. By investigating the effect of 104,105Mo beta-decay on the formation of 104,105Tc carbonyl complex, we estimated the lower reaction time limit for the metal carbonyl synthesis in the gas phase to be more than 100 ms. We examined further the influence of the wall material of the recoil chamber, the carrier gas composition, the gas flow rate, and the pressure on the production yield of 104Mo(CO)6, so that the future stability tests with Sg(CO)6 can be optimized accordingly.

A new front-end high-resolution sampling board for the new-generation electronics of EXOGAM2 and NEDA detectors

This paper presents the final design and results of the FADC Mezzanine for the EXOGAM (EXOtic GAMma array spectrometer) and NEDA (Neutron Detector Array) detectors. The measurements performed include those of studying the effective number of bits, the energy resolution using HP-Ge detectors, as well as timing histograms and n/γ discrimination performance. Finally, the conclusion shows how a common digitizing device has been integrated in the experimental environment of two very different detectors which combine both low-noise acquisition and fast sampling rates. Not only the integration fulfilled the expected specifications on both systems, but it also showed how a study of synergy between detectors could lead to the reduction of resources and time by applying a common strategy.

A digital front-end electronics for the neutron detector NEDA

This paper presents the design of the NEDA front-end electronics, a first attempt to involve the use of digital electronics in large neutron detector arrays. Among the electronic modules taking part, we emphasize on the front-end analog processing, the digitalization, digital pre-processing, communications firmware, as well as the integration of the Global Trigger and Synchronization system. The NEDA array will be available for measurements in 2015.

γ -ray linear polarization measurements and (g9/2) −3 neutron alignment in 91Ru

The authors would like to thank the operators of the GANIL cyclotrons for providing the 36Ar beam. We would also like to thank the EXOGAM Collaboration for use of the clover Ge detector array, the DIAMANT Collaboration for use of the charged particle detector system, and the European gamma-ray Spectroscopy Pool for use of the neutron detector system. We acknowledge funding support from the French-Polish LEA COPIGAL and the IN2P3-Polish laboratories COPIN Agreement No. 06-122, from the UK STFC, from the Swedish Research Council (Contracts No. 2007-4067 and No. 2008-5793), from the Goran Gustafsson Foundation, from the OTKA under Contract No. K100835, and from the Bolyai Janos Foundation. AG has been supported by the Generalitat Valenciana, Spain, under Grant No. PROMETEO/2010/101 and by MINECO, Spain, under Grants No. AIC-D-2011-0746 and No. FPA2011-29854. AJ acknowledge financial support from the Spanish Ministerio de Ciencia e Innovacion under Contract No. FPA2011-29854-C04. ZY acknowledges the support from the Chinese Academy of Sciences, China.

Evaporation channel as a tool to study fission dynamics

Abstract The dynamics of the fission process is expected to affect the evaporation residue cross section because of the fission hindrance due to the nuclear viscosity. Systems of intermediate fissility constitute a suitable environment for testing such hypothesis since they are characterized by evaporation residue cross sections comparable or larger than the fission ones. Observables related to emitted charged particles, due to their relatively high emission probability, can be used to put stringent constraints on models describing the excited nucleus decay and to recognize the effects of fission dynamics. In this work model simulations are compared with the experimental data collected via the S 32 + 100 Mo reaction at E lab = 200  MeV . Consequently we pointed out, exploring an extended set of evaporation channel observables, the limits of the statistical model and the large improvement obtained with a dynamical model. Moreover we stress the importance of using an apparatus covering a large fraction of 4π to extract observables. Finally, we discuss the opportunity to measure more sensitive observables by a new detection device in operation at LNL.

ALBEGA: A Decay Spectroscopy Setup for Chemically Separated Samples

Di Nitto, A.; Yakushev, A.; Düllmann, C. E.; Khuyagbaatar, J.; Krier, J.; Ballof, J.; Bar, J.; Budzynski, T.; Cox, D. M.; Derkx, X.; Dormand, J.; Despotopulos, J. D.; Eberhardt, K.; Even, J.; Grabiec, P.; Harkness-Brennan, L.; Herzberg, R. D.; Hübner, A.; Jäger, E.; Judson, D.; Kindler, B.; Klos, H.; Kratz, J. V.; Kulawik, J.; Kurz, N.; Lens, L.; Lommel, B.; Moody, K.; Panas, A.; Prokaryn, P.; Rudolph, Dirk; Runke, J.; Rusanov, I.; Scharrer, P.; Schausten, B.; Shaughnessy, D.; Szmigiel, D.; Ward, A. J.; Wegrzecki, M. Published in: GSI Report

Clustering effects in 48Cr composite nucleus produced via the reaction 24Mg + 24Mg at the excitation energy of 60 MeV

The reaction 24Mg + 24Mg was used to produce the composite nucleus 48Cr at 60 MeV of excitation energy where a narrow resonance (170 KeV) has been found by measuring the elastic and inelastic channels. To determine the occurrence of deformation of this compound nucleus and its possible connection with the resonances and the hypothetical cluster structure, evaporative Light Charged Particles (LCP) were measured and compared to Statistical Model (SM) predictions. The experiment was performed at LNL using the 8πLP apparatus. The comparison of the evaporation residue-LCP coincidence angular distributions and LCP energy spectra with SM calculations supports the presence of a very large deformation of the composite nucleus 48Cr that scales with the angular momentum.

Identification of Reaction Products in 50Ti+249Cf Reactions at TASCA

The neutron-rich nuclei 33P and 33S in the upper sd-shell were investigated by means of the 26Mg(13C,npa) and 26Mg(13C,2na) fusion-evaporation reactions. Excited states with intermediate and high spins have been populated. The level schemes of both nuclei have been considerably extended. Utilizing the gammagamma-angular correlation method the spin-parity assignment of the new excited states in 33P has been investigated. The experimentally determined energy levels as well as the known reduced transition probabilities (i.e. B(M1) and B(E2) values) from both nuclei were compared to 0hbaromega and 1hbaromega truncated p-sd-pf shell-model calculations using the PSDPF interaction. For the energy levels a very good agreement between experiment and theory was shown for both 33P and 33S. However, for B(M1) and B(E2) values the calculated values cannot reproduce the experimental results with satisfying agreement for all transitions. In some places the discrepancy between experiment and theory is even large, which requires further experimental as well as theoretical investigation of this thesis for these nuclei. The second part was focused on the upgrade and commissioning tests of the Lund- York-Cologne CAlorimeter (LYCCA). As a key device of the High resolution In-flight SPECtroscopy (HISPEC) campaign of the FAIR/NUSTAR collaboration, LYCCA was designed to identify the reaction products after the secondary target, as well as to track the particle trajectory event by event. After the successful employment of the precursor LYCCA-0 in the PreSPEC campaign, the electronic as well as mechanic components of the LYCCA system were upgraded by STFC Daresbury Laboratory. Using the high integrated AIDA Front-End electronics with ASICs the signals from more than thousand DSSSD-channels were pre-amplified and processed. Since 2016, the new LYCCA setup is located at the Cologne tandem accelerator. Triple-Alpha tests and in-beam experiments of elastic scattering were carried out to check the specifications of the system after the upgrade. The obtained results allow first important conclusions about energy resolution and efficiency of the calorimeter at low energies for future NUSTAR experiments.Di Nitto, A.; Khuyagbaatar, J.; Ackermann, D.; Adamczewski-Musch, J.; Andersson, LiseLotte; Badura, E.; Block, M; Brand, H.; Cox, D. M.; Düllmann, Ch. E.; Dvorak, J.; Eberhardt, K.; Ellison, P. A.; Esker, N. E.; Even, J.; Fahlander, Claes; Forsberg, Ulrika; Gates, J.M.; Golubev, Pavel; Gothe, O.; Gregorich, K.E.; Hartmann, W.; Herzberg, R.-D.; Heßberger, F. P.; Hoffmann, J.; Hollinger, R.; Hübner, A.; Jäger, E.; Jeppsson, J.; Kindler, B.; Klein, S.; Kojouharov, I.; Kratz, J.V.; Krier, J.; Kurz, N.; Lahiri, S.; Linev, S.; Lommel, B.; Maiti, M.; Mändl, R.; Merchán, E.; Minami, S.; Mistry, A. K.; Mokry, Ch.; Nitsche, H.; Omtvedt, J. P.; Pang, G.; Pysmenetska, I.; Renisch, D.; Rudolph, Dirk

Recoil-alpha-fission and Recoil-alpha-alpha-fission Chains Stemming from Element 115

Rudolph, Dirk; Forsberg, Ulrika; Düllmann, C. E.; Golubev, Pavel; Heßberger, F.P.; Khuyagbaatar, J.; Kratz, J. V.; Sarmiento, Luis; Yakushev, A.; Ackermann, D.; Andersson, L.; Block, M.; Brand, H.; Cox, D.; Derkx, X.; Di Nitto, A.; Eberhardt, K.; Even, J.; Fahlander, Claes; Gates, J. M.; Gerl, J.; Gregorich, E. K.; Gross, C. J.; Herzberg, R.-D.; Jäger, E.; Kindler, B.; Krier, J.; Kojouharov, I.; Kurz, N.; Lommel, B.; Mistry, A.; Mokry, C.; Nitsche, H.; Omtvedt, J. P.; Papadakis, P.; Runke, J.; Rykaczewski, K.; Schädel, M.; Schaffner, H.; Schausten, B.; Thörle-Pospiech, P.; Torres, T.; Traut, T.; Trautmann, N.; Türler, A.; Ward, A.; Wiehl, N. Published in: GSI Report