Christoph E Düllmann

Christoph E Düllmann
Johannes Gutenberg-Universität Mainz | JGU · Department of Chemistry

Prof. Dr.

About

277
Publications
41,386
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6,204
Citations
Additional affiliations
November 2010 - present
GSI Helmholtzzentrum für Schwerionenforschung
Position
  • Head of Department
February 2010 - present
Helmholtz Institut Mainz
Position
  • Head of Research Section

Publications

Publications (277)
Article
Full-text available
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 hal...
Chapter
The heaviest chemical elements in the periodic table are all artificial, manmade elements, produced one atom at a time at accelerator facilities by fusing nuclei of lighter elements. Following the actinide series, they are called the transactinides and are all radioactive and transform rather quickly - with a few exceptions with half-lives of the o...
Article
Full-text available
Motivated by the challenge of identifying intruder ions in a cold ion crystal, we investigate calorimetry from emitted fluorescence light. Under continuous Doppler cooling, the ion crystal reaches a temperature equilibrium with a fixed level of fluorescence intensity and any change in the motional energy of the crystal results in a modification of...
Article
Full-text available
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
Full-text available
The atomic structure of californium is probed by two-step resonance ionization spectroscopy. Using samples with a total amount of about 2×1010 Cf atoms (ca. 8.3 pg), ground-state transitions as well as transitions to high-lying Rydberg states and auto-ionizing states above the ionization potential are investigated and the lifetimes of various atomi...
Presentation
Full-text available
Chemical studies are a hot and challenging topic in the superheavy element (SHE) research field. The drastically decreasing production cross sections and half-lives with increasing proton number result in a small number of detected events. The chemical study of volatile superheavy elements Cn (Z = 112) and Fl (Z = 114), which have closed electron-s...
Article
Full-text available
The ECHo experiment aims at determining the effective electron neutrino mass by analyzing the endpoint of the ¹⁶³ Ho electron capture spectrum. High energy resolution detectors with a well-tailored detector response are the essential ingredient for the success of the ECHo experiment. Metallic magnetic calorimeter arrays enclosing ¹⁶³ Ho have been c...
Article
Full-text available
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...
Article
Full-text available
We introduce a novel thick-target concept tailored to the extraction of refractory 4d and 5d transition metal radionuclides of molybdenum, technetium, ruthenium and tungsten for radioactive ion beam production. Despite the more than 60-year old history of thick-target ISOL mass-separation facilities like ISOLDE, the extraction of these most refract...
Preprint
Full-text available
Motivated by the challenge of identifying intruder ions in a cold ion crystal, we investigate calorimetry from emitted fluorescence light. Under continuous Doppler cooling, the ion crystal reaches a temperature equilibrium with a fixed level of fluorescence intensity and any change in the motional energy of the crystal results in a modification of...
Article
Full-text available
We implement three-dimensional polarization gradient cooling (PGC) of trapped ions. Counter-propagating laser beams near393nm impinge in lin ⊥ lin configuration, at a frequency below the S 1/2 to P 3/2 resonance in ⁴⁰ Ca ⁺ . Our measurements demonstrate that cooling with laser beams detuned to lower frequencies from the resonance is robust against...
Article
The thick-target ISOL (Isotope mass Separation OnLine) method provides beams of more than 1000 radionuclides of 74 elements. The method is well established for elements with sufficiently high volatility at ca. 2000 °C. To extract non-volatile elements the formation of a volatile molecule is required. While successful in some cases ( e.g. carbon or...
Preprint
The masses of the lightest atomic nuclei and the electron mass are interlinked and are crucial in a wide range of research fields, with their values affecting observables in atomic, molecular and neutrino physics as well as metrology. The most precise values for these fundamental parameters come from Penning-trap mass spectrometry, which achieves r...
Article
The ECHo experiment has been designed for the determination of the effective electron neutrino mass by means of the analysis of the end-point region of the ¹⁶³Ho electron capture spectrum. Metallic magnetic calorimeters enclosing ¹⁶³Ho are used for the high energy resolution calorimetric measurement of the ¹⁶³Ho spectrum. For the first phase of the...
Article
Chemical synthesis typically draws on the roughly 90 elements found in nature and transforms them into fantastic things, which serve all imaginable needs of humankind. However, there are more than just these 90 elements in the periodic table. The synthesis of the heaviest elements, one atom at a time, is discussed here.
Article
Superheavy elements are produced via fusion reactions, by bombarding thin target foils with intense beams of energetic ions with energies around the Coulomb barrier. Currently, production of rare isotopes relies mainly on the molecular plating (MP) method, which yields thin films of the desired target material on a backing foil. Intense heavy-ion b...
Article
In 2014 the first synthesis of a transactinide carbonyl complex – seaborgium hexacarbonyl – was reported. This was achieved in gas-phase chemical experiments in a beam-free environment behind the recoil separator GARIS. Extending this work to heavier elements requires more efficient techniques to synthesize carbonyl complexes as production rates of...
Article
Full-text available
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...
Preprint
The ECHo experiment has been designed for the determination of the effective electron neutrino mass by means of the analysis of the end-point region of the Ho-163 electron capture spectrum. Metallic magnetic calorimeters enclosing Ho-163 are used for the high energy resolution calorimetric measurement of the Ho-163 spectrum. For the first phase of...
Article
A novel combination of advanced gas-chromatography and detection systems coupled to a buffer-gas cell was characterized on-line to allow gas-phase chemical studies of accelerator-produced short-lived α-decaying mercury, francium, and astatine isotopes. These were produced in ⁴⁰Ar- and ⁴⁸Ca-induced nuclear fusion–evaporation reactions, subsequently...
Preprint
Full-text available
The thick-target ISOL (Isotope mass Separation OnLine) method provides beams of more than 1000 radionuclides of 74 elements. The method is well established for elements with sufficiently high volatility at ca. 2000 {\deg}C. To extract non-volatile elements the formation of a volatile molecule is required. While successful in some cases (e.g. carbon...
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...
Preprint
Full-text available
We implement three-dimensional polarization gradient cooling of trapped ions. Counter-propagating laser beams near 393 nm impinge in lin ⊥ lin configuration, at a frequency below the S 1/2 to P 3/2 resonance in 40 Ca +. We demonstrate mean phonon numbers of 5.4(4) at a trap frequency of 2π × 285 kHz and 3.3(4) at 2π × 480 kHz, in the axial and radi...
Preprint
Full-text available
We implement three-dimensional polarization gradient cooling of trapped ions. Counter-propagating laser beams near $393\,$nm impinge in lin$\,\perp\,$lin configuration, at a frequency below the S$_{1/2}$ to P$_{3/2}$ resonance in $^{40}$Ca$^+$. We demonstrate mean phonon numbers of $5.4(4)$ at a trap frequency of $2\pi \times 285\,$kHz and $3.3(4)$...
Preprint
Full-text available
We introduce a novel thick-target concept tailored to the extraction of refractory 4d and 5d transition metal radionuclides of molybdenum, technetium, ruthenium and tungsten for radioactive ion beam production. Despite the more than 60-year old history of thick-target ISOL mass-separation facilities like ISOLDE, the extraction of the most refractor...
Article
Measurements of mass and angular distributions have been made for fission-like outcomes in reactions forming isotopes of flerovium (Z=114), using ⁴⁸Ca, ⁵⁰Ti, and ⁵⁴Cr projectiles. The dominant fast quasifission process, which masks the presence of fusion-fission, has minimum yield at the most backward angles, where the sensitivity to fusion-fission...
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
We present a new system, which is suitable for performing fast liquid phase chemistry experiments and gives access to shorter-lived isotopes of super heavy elements (SHE) than accessible with current techniques. With this novel vacuum to liquid transfer chamber (VLTC), which is mounted behind a physical preseparator, the desired isotopes are transp...
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...
Article
To study the chemical properties of the heaviest elements, a fast and efficient stopping and extraction of the highly energetic residues from heavy ion fusion reactions into the chemistry setup is essential. Currently used techniques like Recoil Transfer Chambers (RTC) relying on gas flow extraction provide high efficiencies for chemically non-reac...
Article
The development of a setup for a fast online characterization of radionuclide generators is reported. A generator utilizing the mother nuclide ²²⁷ Ac sorbed on a cation exchange resin is continuously eluted by using a peristaltic pump. To allow continuous and pulse-free elution of a large volume over extended time periods a 3D-printed interface des...
Article
Full-text available
A nuclear spectroscopy experiment was conducted to study α-decay chains stemming from isotopes of flerovium (element Z=114). An upgraded TASISpec decay station was placed behind the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. The fusion-evaporation reactions Ca48+Pu242 and Ca48+Pu244 provid...
Article
The formation of carbonyl complexes using atom-at-a-time quantities of short-lived transition metals from fusion and fission reactions was reported in 2012. Numerous studies focussing on this chemical system, which is also applicable for the superheavy elements followed. We report on a novel two-chamber approach for the synthesis of such complexes...
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
Full-text available
The specific heat of dilute alloys of holmium in gold and in silver plays a major role in the optimization of low temperature microcalorimeters with enclosed 163Ho, such as the ones developed for the neutrino mass experiment ECHo. We investigate alloys with atomic concentrations of xHo=0.01-4% at temperatures between 10 and 800mK. Due to the large...
Article
A search for production of the superheavy elements with atomic numbers 119 and 120 was performed in the 50Ti+249Bk and 50Ti+249Cf fusion-evaporation reactions, respectively, at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. Over four months of irradiation, the 249Bk target partially decayed into 249Cf, which allowed for a simultan...
Article
Full-text available
Ions of the isomer 229mTh are a topic of high interest for the construction of a “nuclear clock” and in the field of fundamental physics for testing symmetries of nature. They can be efficiently captured in Paul traps which are ideal for performing high precision quantum logic spectroscopy. Trapping and identification of long-lived ²³²Th⁺ ions from...
Article
Full-text available
Resonance ionization mass spectroscopy has proven to be a very efficient and selective method for the spatially resolved ultratrace determination of actinide contaminations, and the analysis of specific element and isotopic distributions on surfaces and environment particles. We report on the identification of highly element-selective optical excit...
Article
Full-text available
An upgraded TASISpec setup, with the addition of a veto DSSD and the new Compex detector-germanium array, has been employed with the gas-filled recoil separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung Darmstadt, to study flerovium (element 114) decay chains. The detector upgrades along with development of new analytical technique...
Article
Full-text available
Four different techniques were applied for the production of 233 U alpha recoil ion sources, providing 229 Th ions. They were compared with respect to a minimum energy spread of the 229 Th recoil ions, using the emitted alpha particles as an indicator. The techniques of Molecular Plating, Drop-on-Demand inkjet printing, chelation from dilute nitric...
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
We present a measurement of the low-energy (0–60 keV) γ-ray spectrum produced in the α decay of 233U using a dedicated cryogenic magnetic microcalorimeter. The energy resolution of ∼10 eV, together with exceptional gain linearity, allows us to determine the energy of the low-lying isomeric state in 229Th using four complementary evaluation schemes....
Article
Full-text available
The masses of the lightest atomic nuclei and the electron mass¹ are interlinked, and their values affect observables in atomic², molecular3–5 and neutrino physics⁶, as well as metrology. The most precise values for these fundamental parameters come from Penning trap mass spectrometry, which achieves relative mass uncertainties of the order of 10⁻¹¹...
Article
We report on cyclotron frequency measurements on trapped 206,207Pb⁺ ions by means of the non-destructive Fourier-transform ion-cyclotron-resonance technique at room temperature. In a proof-of-principle experiment using a quartz crystal instead of a coil as a resonator, we have alternately carried out cyclotron frequency measurements for ²⁰⁶Pb⁺ and...
Article
Full-text available
Background: Cross sections for the formation of superheavy elements (SHE) by heavy ion fusion are suppressed by the competing quasifission process. This results in a fissionlike decay after capture but before formation of a compact compound nucleus. Fast quasifission is evident from very mass-asymmetric fission, focused in angle. In contrast, slow...
Article
Full-text available
An active fission target has been developed for the FIPPS instrument at ILL, enabling for the first time an efficient suppression of β-delayed γ rays in high-resolution and high-efficiency γ-ray spectroscopy of fission fragments at a neutron beam. The target is based on a liquid scintillator in which the actinide is dissolved, resulting in a 4π fra...
Article
Full-text available
The synthesis of new superheavy elements beyond oganesson (Z=118) requires fusion reactions with projectile nuclei with proton numbers larger than that of ⁴⁸Ca (Z=20), which has been successfully employed for the synthesis of elements with Z=112-118. In such reactions, fusion is drastically hindered by fast non-equilibrated dynamical processes. Att...
Preprint
We present a measurement of the low-energy (0--60$\,$keV) $\gamma$ ray spectrum produced in the $\alpha$-decay of $^{233}$U using a dedicated cryogenic magnetic micro-calorimeter. The energy resolution of $\sim$$10\,$eV, together with exceptional gain linearity, allow us to measure the energy of the low-lying isomeric state in $^{229}$Th using four...
Article
We report on the successful coupling of the Penning-trap mass spectrometry setup TRIGA-TRAP to the research reactor TRIGA Mainz. This offers the possibility to perform direct high-precision mass measurements of short-lived nuclei produced in neutron-induced fission of a 235U target located near the reactor core. An aerosol-based gas-jet system is u...
Preprint
Four different techniques were applied for the production of 233U alpha recoil ion sources, providing 229Th ions. They were compared with respect to a minimum energy spread of the 229Th recoil ions, using the emitted alpha particles as an indicator. The techniques of Molecular Plating, Drop-on-Demand inkjet printing, chelation from dilute nitric ac...
Article
At the end of August 2019, the 6th international conference on the chemistry and physics of the transactinide elements (TAN 19) took place in Wilhelmshaven. About 130 researchers from 19 countries on 4 continents gathered to discuss all experimental and theoretical aspects of this multifaceted science field. On six days, the scientists presented th...
Preprint
Full-text available
The specific heat of dilute holmium alloys plays a major role in the optimization of low temperature microcalorimeters with enclosed $^{163}\textrm{Ho}$, such as the ones developed for the neutrino mass experiment ECHo. We investigate alloys with atomic concentrations of $x_\textrm{Ho}=0.01\,\% - 4\,\%$ at temperatures between $10\,\textrm{mK}$ and...
Article
This paper reports on the development and testing of a novel, highly efficient technique for the injection of very rare species into electron beam ion traps (EBITs) for the production of highly charged ions (HCI). It relies on in-trap laser-induced desorption of atoms from a sample brought very close to the electron beam resulting in a very high ca...
Article
Full-text available
Abstract The determination of the effective electron neutrino mass via kinematic analysis of beta and electron capture spectra is considered to be model-independent since it relies on energy and momentum conservation. At the same time the precise description of the expected spectrum goes beyond the simple phase space term. In particular for electro...
Article
A table top setup was developed for the irradiation of thin layers with low-energy electrons and ions of gaseous species. This serves to gain a better understanding of the chemical microprocesses involved during irradiations. The gained insights will complement the understanding of heavy-ion beam induced transformations at on-line facilities and wi...
Preprint
Full-text available
Ions of the isomer $^{229m}$Th are a topic of high interest for the construction of a "nuclear clock" and in the field of fundamental physics for testing symmetries of nature. They can be efficiently captured in Paul traps which are ideal for performing high precision quantum logic spectroscopy. Trapping and identification of long-lived $^{232}$Th$...
Preprint
This paper reports on the development and testing of a novel, highly efficient technique for the injection of very rare species into electron beam ion traps (EBITs) for the production of highly charged ions (HCI). It relies on in-trap laser-induced desorption of atoms from a sample brought very close to the electron beam resulting in a very high ca...
Article
Full-text available
The production of selenium ion beams has been investigated at the CERN-ISOLDE facility via two different ionization methods. Whilst molecular selenium (SeCO) beams were produced at ISOLDE since the early 1990s, recent attempts at reliably reproducing these results have so far been unsuccessful. Here we report on tests of a step-wise resonance laser...
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
Full-text available
Owing to its low excitation energy and long radiative lifetime, the first excited isomeric state of thorium-229, 229mTh, can be optically controlled by a laser1,2 and is an ideal candidate for the creation of a nuclear optical clock³, which is expected to complement and outperform current electronic-shell-based atomic clocks⁴. A nuclear clock will...
Article
The effective electron neutrino mass measurement in the framework of the ECHo experiment requires radiochemically pure ¹⁶³Ho, which is ion implanted into detector absorbers. To meet the project specifications in efficiency and purity, the entire process chain of ionization, isotope separation, and implantation of ¹⁶³Ho was optimized. A new two-step...
Article
Background: About 50% of the heavy elements are produced in stars during the slow neutron capture process. The analysis of branching points allows us to set constraints on the temperature and the neutron density in the interior of stars.
Article
Superheavy elements are formed in fusion reactions which are hindered by fast nonequilibrium processes. To quantify these, mass-angle distributions and cross sections have been measured, at beam energies from below-barrier to 25% above, for the reactions of Ca48, Ti50, and Cr54 with Pb208. Moving from Ca48 to Cr54 leads to a drastic fall in the sym...
Article
Some highlight examples on the study of production and chemical properties of heaviest elements carried out mostly at GSI Darmstadt are presented. They focus on the production of some of the heaviest known elements ( 114 Fl, 115 Mc, and 117 Mc), studies of non-fusion reactions, and on chemical studies of 114 Fl. This is the heaviest element, for wh...
Preprint
The first nuclear excited state of $^{229}$Th offers the unique opportunity for laser-based optical control of a nucleus. Its exceptional properties allow for the development of a nuclear optical clock which offers a complementary technology and is expected to outperform current electronic-shell based atomic clocks. The development of a nuclear clo...