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)
. 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)
and W(CO)
. 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
Mo beta-decay on
the formation of
Tc 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
Mo(CO)
, so that the future
stability tests with Sg(CO)
can be optimized accordingly.
Muonic atoms have been used to extract the most accurate nuclear charge radii based on the detection of X-rays from the muonic cascades. Most stable and a few unstable isotopes have been investigated ...with muonic atom spectroscopy techniques. A new research project recently started at the Paul Scherrer Institut aims to extend the highresolution muonic atom spectroscopy for the precise determination of nuclear charge radii and other nuclear structure properties of radioactive isotopes. The challenge to combine the high-energy muon beam with small quantity of stopping mass is being addressed by developing the concept of stopping the muon in a high-density, a high-pressure hydrogen cell and subsequent transfer of the muon to the element of interest. Status and perspectives of the project will be presented.
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The adsorption behavior of
197
Hg and
183–185
Hg on red amorphous selenium (red a-Se) and trigonal selenium (t-Se) was investigated experimentally by off-line and on-line gas chromatographic methods, ...in preparation of a sensitive chemical separation and characterization of the transactinides copernicium (Cn, Z = 112) and flerovium (Fl, Z = 114). Monte-Carlo simulations of a diffusion controlled deposition were in good agreement with the experimental results, assuming as interaction limits −ΔH
ads
red a-Se
(Hg) > 85 kJ/mol, and −ΔH
ads
t-Se
(Hg) < 60 kJ/mol. Both Se allotropes can be used as stationary surfaces in comparative gas-chromatographic chemical investigations of Cn and Fl.
A new method of intermetallic target preparation is described. Based on the molecular plating technique followed by “coupled reduction”, this method allows producing stable and homogeneous metallic ...targets for high intensity irradiations. In the first step, the target material is electroplated on a noble metal surface, ensuring homogeneous distribution of the desired element on the target backing. In the second step, the foil with the plated material is heated in a hydrogen flow. Due to the formation of an intermetallic compound with the noble metal support, reduction of the target material with hydrogen at high temperatures becomes thermodynamically possible.
Nitrates of all six investigated elements (U, Th, Am, Gd, Nd, and Eu) were electroplated with excellent yields on Pd backing foils by the molecular plating technique and completely reduced in hydrogen atmosphere. A homogeneous distribution of the target material over the whole thickness of the Pd foil was observed suggesting a pronounced diffusion of the reduced metals into the backing material already during the reduction process. A first test irradiation experiment with a thin 3.5μm U/Pd intermetallic target is described.
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The thermal release rate of nuclear reaction products was investigated in offline annealing experiments. This work was motivated by the search for a high melting catcher material for recoiling ...products from heavy ion induced nuclear fusion reactions. Polycrystalline refractory metal foils of Ni, Y, Zr, Nb, Mo, Hf, W, and Re were investigated as catcher metals. Diffusion data for various tracer/host combinations were deduced from the measured release rates. This work focuses on the diffusion and the release rate of volatile p-elements from row 5 and 6 of the periodic table as lighter homologues of the superheavy elements with Z⩾113 to be studied in future experiments. A massive radiation damage enhancement of the diffusion velocity was observed. Diffusion trends have been established along the groups and rows of the periodic table based on the dependence of diffusion velocity on atomic sizes.
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In preparation for the experimental investigation of chemical properties of element 112 model studies were conducted based on the assumed similarity of element 112 to either the noble gas Rn or the ...transition metal Hg, its supposed lighter homologue in group 12. The adsorption behavior of elemental Hg on the transition metals Ag, Au, Ni, Pd, and Pt were investigated experimentally by off-line gas thermochromatography. The deduced adsorption data of Hg were compared with new values calculated using the Eichler–Miedema model. The observed sequence of increasing Hg-metal-interactions for Ag < Ni < Au < Pd < Pt confirms the predicted trend. The only exception was Pd, on which Hg was calculated to adsorb at a higher temperature than on Pt. Difficulties to obtain reproducible clean surfaces of Ag, Ni, Pd, and Pt led to the choice of Au as the best metal surface suitable to adsorb Hg.
For fast on-line gas thermochromatography studies on metallic surfaces a new set-up was developed based on the
Volatilization and On-line detection technique (IVO). This set-up was tested in on-line thermochromatographic investigations with short-lived Hg isotopes and
Rn, using Au or Pd as stationary surfaces. An overall efficiency of about 60% and a transportation time less than 25 s was determined for this newly designed IVO. A separation factor of more than 10
was estimated for non-volatile species.
Two experiments aiming at the chemical investigation of element 112 produced in the heavy ion induced nuclear fusion reaction of
Ca with
U were performed at the Gesellschaft für Schwerionenforschung ...(GSI), Darmstadt, Germany. Both experiments were designed to determine the adsorption enthalpy of element 112 on a gold surface using a thermochromatography setup. The temperature range covered in the thermochromatography experiments allowed the adsorption of Hg at about 35 °C and of Rn at about -180 °C. Reports from the Flerov Laboratory for Nuclear Reactions (FLNR), Dubna, Russia claim production of a 5-min spontaneous fission (SF) activity assigned to
112 for the
U(
Ca,3n)
112 reaction. Hence, Experiment I was designed to detect spontaneously fissioning (SF) isotopes of element 112 with half-lives (
) longer than about 20 s. 11 high-energy events were detected. 7 events exhibit a deposition pattern resembling a chromatographic peak in the vicinity of Rn deposition. However, the energy of the events observed in Experiment I was lower than expected for a SF-decay of
112. Therefore, these events could not be unambiguously attributed to the decay of
112. In contradiction with earlier publications newer reports from FLNR Dubna claim that
112 decays by α-particle emission (
= 9.5 MeV) with
= 4 s followed by a SF-decay of
Ds (
= 0.2 s). Therefore, Experiment II was designed to be sensitive to both claimed decay properties of
112. However, during this experiment neither short α-SF correlations nor SF coincidences were detected. The conclusion is that
112 was not unambiguously detected, neither in Experiment I nor in Experiment II.
A custom-made 228Th source of several MBq activities was produced for the Borexino experiment to study the external background of the detector. The aim was to reduce the unwanted neutron emission ...produced via (α,n) reactions in ceramics typically used for commercial 228Th sources. For this purpose a ThCl4 solution was chemically converted into ThO2 and embedded in a gold foil.
The paper describes the production of the custom-made source and its characterization by means of γ-activity, dose rate and neutron source strength measurements. From γ-spectroscopic measurements it was deduced that activity transfer from the initial solution to the final source was >91% (at 68% C.L.) and the final activity was (5.41±0.30) MBq. The dose rate was measured with two dosimeters yielding 12.1mSv/h and 14.3mSv/h in 1cm distance. The neutron source strength of the 5.41MBq 228Th source was determined to be (6.59±0.85) s−1.
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The existence of 𝒫𝒯 symmetric wave functions describing Bose‐Einstein condensates in a one‐dimensional and a fully three‐dimensional double‐well setup is investigated theoretically. When particles ...are removed from one well and coherently injected into the other the external potential is 𝒫𝒯 symmetric. We solve the underlying Gross‐Pitaevskii equation by way of the time‐dependent variational principle (TDVP) and show that the 𝒫𝒯 symmetry of the external potential is preserved by both the wave functions and the nonlinear Hamiltonian as long as eigenstates with real eigenvalues are obtained. 𝒫𝒯 broken solutions of the time‐independent Gross‐Pitaevskii equation are also found but have no physical relevance. To prove the applicability of the TDVP we compare its results with numerically exact solutions in the one‐dimensional case. The linear stability analysis and the temporal evolution of condensate wave functions demonstrate that the 𝒫𝒯 symmetric condensates are stable and should be observable in an experiment.
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