.
The reaction
54
Cr$ + $
248
Cm
was investigated at the velocity filter SHIP at GSI, Darmstadt, with the intention to study production and decay properties of isotopes of element 120. Three ...correlated signals were measured, which occurred within a period of 279ms. The heights of the signals correspond with the expectations for a decay sequence starting with an isotope of element 120. However, a complete decay chain cannot be established, since a signal from the implantation of the evaporation residue cannot be identified unambiguously. Measured properties of the event chain are discussed in detail. The result is compared with theoretical predictions. Previously measured decay properties of even element super-heavy nuclei were compiled in order to find arguments for an assignment from the systematics of experimental data. In the course of this review, a few tentatively assigned data could be corrected. New interpretations are given for results which could not be assigned definitely in previous studies. The discussion revealed that the cross-section for production of element 120 could be high enough so that a successful experiment seems possible with presently available techniques. However, a continuation of the experiment at SHIP for a necessary confirmation of the results obtained in a relatively short irradiation of five weeks is not possible at GSI presently. Therefore, we decided to publish the results of the measurement and of the review as they exist now. In the summary and outlook section we also present concepts for the continuation of research in the field of super-heavy nuclei.
•Thomson's parabola spectrograph.•Aston's high resolution spectrographs.•Nier's spectrometers.•Mattauch-Herzog and Ewald double-focusing high resolution mass spectrographs.•ISOL, recoil, and fragment ...separators for rare-isotopes.•Precision mass measurements in a storage ring.
Mass spectrometry contributed to the understanding of the structure of elementary matter including the isotopic nature of the chemical elements, isotopic abundances, nuclear binding, and the investigation of nuclides far-off stability. In this paper the continuous development of mass spectrometers from W. Wien's first mass analysis to J.J. Thomson's discovery of isotopes, F.W. Aston's mass spectrometers, and the Mattauch–Herzog double focusing spectrometer to the present rare isotope facilities will be discussed. Separators with magnetic sector fields e.g. from A.O. Nier and the Oak Ridge separator batteries for large-scale isotope production are included. The first applications to chemistry and geochemistry will be mentioned briefly. The key role of the development of ion optics from the first geometrical calculations towards modern matrix method is addressed. Finally recent developments of mass spectrometers for basic nuclear research including ISOL and in-flight separators for rare-isotope facilities and mass spectrometry with cooled and stored ions will be presented.
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 region below lead, which was triggered by model calculations. The
γ
,
α
and spontaneous fission activities of the populated nuclides have been analyzed for their identification. The cross-sections of the observed isotopes for elements
Z
=
81–93 as a function of their mass number have been investigated. Excitation energy, total kinetic energy and the influence of nuclear shell effects on the production cross-sections of the observed transfer products have been studied. Also we present a compact review and comparative analysis of various multi-nucleon transfer and fragmentation reactions which are aimed at the synthesis of neutron-rich nuclides along the
N
=
126
shell closure in heavy nuclei.
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 identification was performed via the α decay chains of the nuclei. These first results reveal that multinucleon transfer reactions together with here applied fast and sensitive separation and detection techniques are promising for the synthesis of new isotopes in the region of heaviest nuclei.
Heavy-element research with SHIP at GSI is reviewed including the discovery of the chemical elements bohrium to copernicium, experimental developments, cold fusion of heavy ions, and the discovery of ...a shell region around hassium. Elements bohrium and heavier are located beyond the limit of liquid-drop stability. They exist by shell stabilization. A universal, sensitive, and fast method: in-flight separation and identification of single atomic nuclei has been developed with the velocity filter SHIP and the detector system to measure decay sequences of individual atoms. Research with single atomic nuclei including detection methods, identification, and physics results will be discussed. Experiments with actinide targets as well as prospects with NUSTAR at FAIR will be addressed.
.
Recently, we reported the observation of several new isotopes with proton numbers
in low-energy collisions of
48
Ca +
248
Cm . 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 Nuclides. For separation of the transfer products we used a velocity filter, the Separator for Heavy Ion Reaction Products SHIP at GSI. The resulting strong background suppression allowed us to detect nuclei with cross-sections down to the sub-nanobarn scale. Beside the new isotopes we identified about 100 further target-like transfer products and determined their cross-sections. The results together with previous measurements strongly indicate that multinucleon transfer reactions are a viable pathway to the production of new transuranium isotopes.
The measurements of neutron capture cross sections of neutron-rich nuclei are challenging but essential for understanding nucleosynthesis and stellar evolution processes in the explosive burning ...scenario. In the quest of -process abundances, according to the neutrino-driven-wind model, light neutron-rich unstable nuclei may play a significant role as seed nuclei that influence the abundance pattern. Hence, experimental data for neutron capture cross sections of neutron-rich nuclei are needed. Coulomb dissociation of radioactive ion beams at intermediate energy is a powerful indirect method for inferring capture cross section. As a test case for validation of the indirect method, the neutron capture cross section (, ) for was inferred from the Coulomb dissociation of at intermediate energy ( MeV). A comparison between different theoretical approaches and experimental results for the reaction is discussed. We report for the first time experimental reaction cross sections of , , , and . The reaction cross sections were inferred indirectly through Coulomb dissociation of , , and at incident projectile energies around 400-430 MeV using the FRS-LAND setup at GSI, Darmstadt. The neutron capture cross sections were obtained from the photoabsorption cross sections with the aid of the detailed balance theorem. The reaction rates for the neutron-rich Na, Mg, Al nuclei at typical -process temperatures were obtained from the measured () capture cross sections. The measured neutron capture reaction rates of the neutron-rich nuclei, , , and are significantly lower than those predicted by the Hauser-Feshbach decay model. A similar trend was observed earlier for and but in the case of the trend is opposite. The situation is more complicated when the ground state has a multi-particle-hole configuration. For , the measured cross section is about higher than the Hauser-Feshbach prediction.
The differential cross sections for small-angle proton elastic scattering on the
6,8,9,11Li nuclei at energies near 700 MeV/nucleon were measured in inverse kinematics using secondary nuclear beams ...at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR was employed as target and recoil proton detector. For determining the nuclear matter radii and radial matter distributions, the measured cross sections have been analysed with the aid of the Glauber multiple-scattering theory. The nuclear matter distribution deduced for
11Li exhibits a very pronounced halo structure, the matter radius of
11Li being significantly larger than those of the
6,8,9Li isotopes. The data on
8,9Li are consistent with the existence of sizable neutron skins in these nuclei. The obtained data allow for a test of various theoretical model calculations of the structure of the studied neutron-rich nuclei.
One-neutron knockout reactions from Borromean nuclei are analyzed using a profile function analysis technique. The profile function, which is derived as the square root of the variance of the ...measured fragment + neutron momenta as a function of their relative energy, is shown to be very sensitive to the angular momentum of the knocked out neutron. Three cases are studied here: 7He, where the profile function analysis shows a presence of (s1/2)2 component in the 8He ground-state wave-function, 10Li, where the presence of a 11(2)% d-wave contribution to the relative energy spectrum above 1.5 MeV is found and, finally, the presence of a major s contribution around 0.5 MeV relative energy in the 13Be case and that the observed decay to the 12Be 2+ state originates in a d state in 13Be.
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