F. P. Heßberger's research while affiliated with GSI Helmholtzzentrum für Schwerionenforschung and other places

Publications (387)

Article
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Flerovium (Fl, element 114) is the heaviest element chemically studied so far. To date, its interaction with gold was investigated in two gas-solid chromatography experiments, which reported two different types of interaction, however, each based on the level of a few registered atoms only. Whereas noble-gas-like properties were suggested from the...
Article
The decay of excited states in 255No was investigated by applying the evaporation-residue–conversion-electron correlation technique. Two new isomeric states were observed in 255No together with the previously known one. Excitation energies of the isomeric states were estimated based on the energies of conversion electrons and γ rays from correlatio...
Article
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Superheavy element research has been a strong pillar of the research program at GSI Darmstadt since its foundation. Six new elements were discovered along with many new isotopes. Initial results on chemical properties of the heaviest elements were obtained that allowed for comparing their behavior with that of their lighter homologs and with theore...
Preprint
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Velocity distributions of heavy residues (A_Res > A_Tar), produced in irradiations of Au-197 and Ho-165 with Ne-20 at bombarding energies of E = 208 MeV, have been measured at the velocity filter SHIP. While for the products from Ne-20 + Ho-165 just a mean value of v/v_CN = 0.91+-0.01 was obtained, individual residues, attributed to isotopes of ast...
Article
Alpha decay and spontaneous fission of the ground-state and the isomeric state of $$^{247}$$ 247 Md were investigated with specific emphasis to identify the ground-state of the daughter nucleus $$^{243}$$ 243 Es. The decay studies were accompanied by measuring $$\alpha $$ α - $$\gamma $$ γ coincidences. On the basis of the measured data an improved...
Article
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Nihonium (Nh, element 113) and flerovium (Fl, element 114) are the first superheavy elements in which the 7p shell is occupied. High volatility and inertness were predicted for Fl due to the strong relativistic stabilization of the closed 7p 1/2 sub-shell, which originates from a large spin-orbit splitting between the 7p 1/2 and 7p 3/2 orbitals. On...
Article
In the heaviest elements, the instability of atomic nuclei against spontaneous fission leads to ever shorter nuclear half-lives. Upon falling below a timescale of 10−14 s, the border of existence of isotopes is crossed because this is the timescale on which the formation of atomic shells occurs. Analysis of the experimental data on the spontaneous...
Article
The question of the number and origin of isomeric states in Rf256 arose from two independent experiments but remained unanswered for a decade. To shed light on this puzzle, we studied isomeric decay in Rf256 by measuring conversion electrons with fast fully digital electronics. Rf256 was produced in the fusion-evaporation reactions of Ti50+Pb207 an...
Article
In two recent papers by Pore et al. and Khuyagbaatar et al., discovery of the new isotope Md244 was reported. The decay data, however, are conflicting. While Pore et al. report two isomeric states decaying by α emission with Eα(1)=8.66(2) MeV, T1/2(1)=0.4−0.1+0.4 s and Eα(2)=8.31(2) MeV, T1/2(2)≈6 s, Khuyagbaatar et al. [Phys. Rev. Lett. 125, 14250...
Preprint
Full-text available
Synthesis of new elements at the upper border of the charts of nuclei and investigation of their decay properties and nuclear structure has been one of the main research topics in low energy nuclear physics since more than five decades. Main items are the quest for the heaviest nuclei that can exist and the verification of the theoretical predicted...
Preprint
In two recent papers by Pore et al. and Khuyagbaatar et al. discovery of the new isotope Md-244 was reported. The decay data, however, are conflicting. While Pore et al. report two isomeric states decaying by alpha emission with E(1)=8.66(2) MeV, T_1/2=0.4+0.4/-0.1s and E(2)=8.31(2) MeV, T_1/2 approx 6 s, Khuyagbaatar et al. report only a single tr...
Article
Nuclear structure of Fm243, Fm245, and their daughter nuclei were investigated via detection of their radioactive decays, α, γ, and spontaneous fission. Measured α-decay energies, half-lives, and branching ratios improve the literature data significantly. A signature for detection of the hitherto unknown Cm235 was found in the α-decay chains from F...
Preprint
The electron-capture decay followed by a prompt fission process was searched for in the hitherto unknown most neutron-deficient Md isotope with mass number 244. Alpha decay with α-particle energies of 8.73–8.86 MeV and with a half-life of 0.30−0.09+0.19 s was assigned to Md244. No fission event with a similar half-life potentially originating from...
Article
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We present new results on multi-nucleon transfer reactions in low-energy collisions of 48 Ca+ 238 U measured at the velocity filter SHIP of GSI Helmholtz Centre, where we observed around 90 different nuclides from Tl to Am (Z = 81-95). We followed the idea to use uranium targets for the synthesis of neutron-rich MNT products, particularly in the re...
Article
Spontaneous fission properties of the isotopes Rf255, Rf256, and Rf258 produced in the reactions Ti50+Pb207, Ti50+Pb208, and Ti50+Bi209 were studied. The method of time and position correlations was used to identify spontaneous fission events. The correction to the energy deficit in measured total kinetic energy (TKE) determined on the basis of a s...
Article
Decay spectroscopy of No250 has been performed using digital electronics and pulse-shape analysis of the fast nuclear decays for the first time. Previous studies of No250 reported two distinct fission decay lifetimes, related to the direct fission of the ground state and to the decay of an isomeric state but without the possibility to determine if...
Article
Full-text available
Background: The neutron-deficient lead region provides a range of nuclear phenomena, including isomerism at low energies. This phenomenon can be studied by α decay because the degree of hindrance of α decay provides information on the change in nuclear structure of connected states.
Article
Experimental data on evaporation residue production in the reaction ⁵⁰Ti + ²⁰⁹Bi \(\rightarrow\)²⁵⁹Db* measured at SHIP in the excitation energy range \( E^{\ast} = 11-31\) MeV were reanalyzed with respect to search for products from pxn-deexcitation channels. While most of the measurements resulted only in upper cross section limits in the range \...
Article
The neutron-deficient isotopes 254,255Rf were produced in the fusion-evaporation reaction ⁵⁰Ti + ²⁰⁶Pb at the gas-filled recoil separator TASCA. Decay properties of these nuclei were investigated by applying fast digital electronics. A search for isomeric states in both isotopes was performed by using the accompanying conversion electron emissions....
Article
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Hyperfine-structure parameters and isotope shifts for the 795-nm atomic transitions in At217,218,219 have been measured at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy technique. Magnetic dipole and electric quadrupole moments, and changes in the nuclear mean-square charge radii, have been deduced. A large inverse odd-even sta...
Article
The heaviest currently known nuclei, which have up to 118 protons, have been produced in Ca48 induced reactions with actinide targets. Among them, the element tennessine (Ts), which has 117 protons, has been synthesized by fusing Ca48 with the radioactive target Bk249, which has a half-life of 327 d. The experiment was performed at the gas-filled r...
Article
Fusion-evaporation reactions with the doubly magic projectile ⁴⁸ Ca were used to access neutron-deficient nuclei around neptunium at the velocity filter SHIP, and investigated using the COMPASS decay spectroscopy station. With the use of digital electronics, several isotopes produced via neutron, proton, and α evaporation channels were identified b...
Article
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After publication of the paper, the authors noticed some errors in the affiliations. Their correct version is given in this erratum.
Article
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The results for nuclei above curium, produced in multi-nucleon transfer reactions of ⁴⁸Ca + ²⁴⁸Cm at the velocity filter SHIP of GSI Darmstadt, are presented. Spontaneous fission and \( \alpha\)-activities have been used to study the population of nuclei with lifetimes ranging from few milliseconds to several days. We observed several, relatively n...
Article
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The superheavy isotope ²⁵⁸Db was produced in the ²⁰⁹Bi(⁵⁰Ti, 1n)²⁵⁸Db reaction at GSI, Germany. A detailed \( \alpha\)-spectroscopy study of this isotope and its \( \alpha\)-decay daughter products was performed. Two long-lived \( \alpha\)-decaying states in ²⁵⁸Db are observed. A spin-parity of \( 0^{-}\) is tentatively assigned to the ground state...
Article
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The isotopes 255,256,258 Rf were produced in the fusion-evaporation reactions ⁵⁰ Ti + 207,208 Pb and ⁵⁰ Ti + ²⁰⁹ Bi at GSI Darmstadt, using the velocity filter SHIP. Total kinetic energies of fragments from spontaneous fission for these isotopes were evaluated with a correction to pulse-height defect.
Article
Short-lived α-decaying nuclei “northeast” of Pb208 in the chart of nuclides were studied using the reaction Ca48+Am243 with the decay station TASISpec at TASCA, GSI Darmstadt. Decay energies and times from pile-up events were extracted with a tailor-made pulse-shape analysis routine and specific α-decay chains were identified in a correlation analy...
Article
Online gas-solid adsorption studies with single-atom quantities of Hg, Tl, and Pb, the lighter homologs of the superheavy elements (SHE) copernicium (Cn, Z =112), nihonium (Nh, Z =113), and flerovium (Fl, Z =114), were carried out using short-lived radioisotopes. The interaction with Au and SiO 2 surfaces was studied and the overall chemical yield...
Article
The isotopic distribution of nuclei produced in the ⁵⁰Ti + ²⁴⁹Cf reaction has been studied at the gas-filled recoil separator TASCA at GSI Darmstadt, which separates ions according to differences in magnetic rigidity. The bombardment was performed at an energy around the Bass barrier and with the TASCA magnetic fields set for collecting fusion-evap...
Article
One of the most important atomic properties governing an element’s chemical behavior is the energy required to remove its least-bound electron, referred to as the first ionization potential. For the heaviest elements, this fundamental quantity is strongly influenced by relativistic effects which lead to unique chemical properties. Laser spectroscop...
Article
Until recently, ground-state nuclear moments of the heaviest nuclei could only be inferred from nuclear spectroscopy, where model assumptions are required. Laser spectroscopy in combination with modern atomic structure calculations is now able to probe these moments directly, in a comprehensive and nuclear-model-independent way. Here we report on u...
Article
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Hyperfine-structure parameters and isotope shifts of At195–211 have been measured for the first time at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy method. The hyperfine structures of isotopes were recorded using a triad of experimental techniques for monitoring the photo-ion current. The Multi-Reflection Time-of-Flight Mass...
Article
A compact silicon detector array with high spatial granularity and fast, fully digital data recording has been developed and commissioned for the investigation of heavy and superheavy nuclear species. The detector array can be combined in close geometry with large volume germanium detectors. It offers comprehensive particle and photon coincidence a...
Article
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The exotic decay process of β-delayed fission (βDF) has been studied in the neutron-deficient isotope Am230. The Am230 nuclei were produced in the complete fusion reaction Pb207(Al27,4n)Am230 and separated by using the GARIS gas-filled recoil ion separator. A lower limit for the βDF probability PβDF(Am230)>0.30 was deduced, which so far is the high...
Article
An experimental scheme combining the mass resolving power of a Penning trap with contemporary decay spectroscopy has been established at GSI Darmstadt. The Universal Linear Accelerator (UNILAC) at GSI Darmstadt provided a Ca48 beam impinging on a thin Er170 target foil. Subsequent to velocity filtering of reaction products in the Separator for Heav...
Article
Using the sensitive Radiation Detected Resonance Ionization Spectroscopy (RADRIS) technique an optical transition in neutral nobelium (No, Z = 102) was identified. A remnant signal when delaying the ionizing laser indicated the influence of a strong buffer gas induced de-excitation of the optically populated level. A subsequent investigation of the...
Article
A sequence of three events observed in an irradiation of ²⁴⁸Cm with ⁵⁴Cr at the velocity filter SHIP of the GSI - Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany, had been interpreted as a decay chain consisting of three α particles. On the basis of measured energies, a possible assignment to the decay of an isotope of elem...
Article
Spontaneous fission properties of transuranium isotopes are reviewed. Specific emphasis was laid on brief historical overviews of theoretical descriptions and experimental determination of basic properties as spontaneous fission half-lives, fission barriers, or total kinetic energy release in fission. Experimental spontaneous fission half-lives are...
Article
With the Penning-trap mass spectrometer SHIPTRAP at GSI, Darmstadt, it is possible to investigate exotic nuclei in the region of the heaviest elements. Few years ago, challenging experiments led to the direct measurements of the masses of neutron-deficient isotopes with Z = 102; 103 around N = 152. Thanks to recent advances in cooling and ion-manip...
Article
Electron capture decay of 258 Db was measured directly via delayed coincidences between K X-rays and/or conversion electrons (from the electron capture decay), and spontaneous fission or \(\alpha\) decay of the daughter nuclide 258Rf. Delayed K X-rays were also measured in prompt coincidence with conversion electrons, showing that electron capture...
Article
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The new neutron-deficient nuclei ²⁴⁰Es and ²³⁶Bk were synthesised at the gas-filled recoil separator RITU. They were identified by their radioactive decay chains starting from ²⁴⁰Es produced in the fusion–evaporation reaction ²⁰⁹Bi(³⁴S,3n)²⁴⁰Es. Half-lives of 6(2)s and 22−6+13s were obtained for ²⁴⁰Es and ²³⁶Bk, respectively. Two groups of α partic...
Article
Optical spectroscopy of a primordial isotope has traditionally formed the basis for understanding the atomic structure of an element. Such studies have been conducted for most elements and theoretical modelling can be performed to high precision, taking into account relativistic effects that scale approximately as the square of the atomic number. H...
Article
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A nuclear-decay spectroscopy study of the neutron-deficient isotope At196 is reported where an isotopically pure beam was produced using the selective Resonance Ionization Laser Ion Source and On-Line Isotope Mass Separator (CERN). The fine-structure α decay of At196 allowed the low-energy excited states in the daughter nucleus Bi192 to be investig...
Article
The experimental determination of atomic levels and the first ionization potential of the heaviest elements ( ) is key to challenge theoretical predictions and to reveal changes in the atomic shell structure. These elements are only artificially produced in complete-fusion evaporation reactions at on-line facilities such as the GSI in Darmstadt at...
Article
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Recently, we reported the observation of several new isotopes with proton numbers \(Z \geq 92\) in low-energy collisions of ⁴⁸Ca + ²⁴⁸Cm . The peculiarity is that the nuclei were produced in multinucleon transfer reactions, a method which is presently discussed as a possible new way to enter so far unknown regions in the upper part of the Chart of...
Article
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A novel rigorous statistical treatment is applied to available data (May 9, 2016) from search and spectroscopy experiments on the elements with atomic numbers Z=115 and Z=117. The present analysis implies that the hitherto proposed cross-reaction link between α-decay chains associated with the isotopes 293117 and 289115 is highly improbable.
Article
Alpha- and Electron capture (EC) decay properties of 257 Rf were investigated by measuring \( \alpha\) - \( \gamma\) coincidences and correlations between conversion electrons (CE) emitted during the process of EC decay of 257Rf and \( \alpha\) decays of the daughter isotope 257Lr. So far, previously unobserved \( \alpha\) (8296 keV)- \( \gamma\) (...
Article
Isomeric states in Po194 and Po192 were studied at the velocity filter SHIP. The isotopes were produced in the fusion-evaporation reactions Pr141(Fe56, p2n)Po194 and Sm144(V51, p2n)Po192. Several new γ-ray transitions were attributed to the isomers and γ−γ coincidences for both isomers were studied for the first time. The 459-keV transition earlier...
Article
Isomeric states in Po194 and Po192 were studied at the velocity filter SHIP. The isotopes were produced in the fusion-evaporation reactions Pr141(Fe56, p2n)Po194 and Sm144(V51, p2n)Po192. Several new γ-ray transitions were attributed to the isomers and γ−γ coincidences for both isomers were studied for the first time. The 459-keV transition earlier...
Article
Products of the fusion-evaporation reaction 48Ca + 243Am were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany. Amongst the detected thirty correlated α-decay chains associated with the production of element Z=115, two recoil-α-fission and five recoil-α-α-fis...
Article
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Superheavy elements owe their stability due to a subtle balance between the disruptive Coulomb force and the attractive nuclear forces. Thus they represent an ideal laboratory to study basic interactions. The essential tools are detailed investigations of radioactive decay properties and nuclear structure of superheavy nuclei. The results of those...
Article
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The fission process still remains a main factor that determines the stability of the atomic nucleus of heaviest elements. Fission half-lives vary over a wide range, 10−19−1024 s. Present experimental techniques for the synthesis of the superheavy elements that usually measure α-decay chains are sensitive only in a limited range of half-lives, often...
Article
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Two short-lived isotopes U221 and U222 were produced as evaporation residues in the fusion reaction Ti50+Yb176 at the gas-filled recoil separator TASCA. An α decay with an energy of Eα=9.31(5) MeV and half-life T1/2=4.7(7) μs was attributed to U222. The new isotope U221 was identified in α-decay chains starting with Eα=9.71(5) MeV and T1/2=0.66(14)...
Article
Significant technical progress concerning the availability of intense heavy-ion beams and highly-efficient and sophisticated detection devices has made nuclear-structure investigations possible in the region of superheavy nuclei. Exciting new results have been obtained by applying α spectroscopy as well as α-γ and internal-conversion-electron coinc...
Article
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We investigated the formation of nuclear molecules and the occurrence of time delays in reactions of the superheavy systems 64Ni + 207Pb ($ Z_{1}+Z_{2}=110$), 132Xe + 208Pb ($ Z_{1}+Z_{2}=136$) and 238U + 238U ($ Z_{1}+Z_{2}=184$. In deep inelastic binary reactions of Ni + Pb and Xe + Pb we observed clear signatures for the formation of long-living...
Conference Paper
New decay data for the isotopes 259Sg and 255Rf were obtained at the velocity filter SHIP using an α-decay spectroscopy measurement. Both isotopes were produced and studied via a one neutron evaporation channel in the compound fusion reaction 54Cr+208 Pb. New isomeric states were observed and the single-particle level systematics for isotones with...
Article
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Mass distributions of fission fragments from the compound nuclei 180Hg and 190Hg formed in fusion reactions 36Ar + 144Sm and 36Ar + 154Sm, respectively, were measured at initial excitation energies of E*(Hg180)=33-66 MeV and E*(Hg190)=48-71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass divis...
Article
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In deep inelastic multinucleon transfer reactions of 48Ca + 248Cm we observed about 100 residual nuclei with proton numbers between Z=82 and Z=100. Among them, there are five new neutron-deficient isotopes: 216U, 219Np, 223Am, 229Am and 233Bk. As separator for the transfer products we used the velocity filter SHIP of GSI while the isotope identific...
Article
Levels in Th223 populated by the α decay of U227 were investigated using α-γ decay spectroscopy. The U227 isotope was produced in the fusion-evaporation reaction Ne22+Pb208 at the velocity filter separator for heavy-ion reaction products at Gesellschaft für Schwerionenforschung in Darmstadt (Germany). Several new excited levels and γ transitions we...