Physicists from the National Center for Nuclear Research and the University of Zielona Góra have determined and reported extremely important parameters for over 1,300 nuclei, including the nuclei of super-heavy elements, which have not been produced in laboratories so far. These results have just been published in the primary reference journal of nuclear physics: Atomic Data and Nuclear Data Tables.
Scientists in many centers around the world are constantly striving to create and research new elements and their isotopes. The main aim of this international race is to discover the still mysterious forces binding atomic nuclei. The research focuses simultaneously on experimental work using powerful accelerators and detectors, as well as on theoretical calculations to identify the most promising production procedure and propose models that can be verified by experiments. Polish scientists have been specializing in this type of theoretical research for several decades, being world leaders, which is clearly confirmed by the extremely extensive and complete work that has just been presented.
Three Polish scientists: Dr. Piotr Jachimowicz from the University of Zielona Góra and Michał Kowal and Janusz Skalski, professors at the National Center for Nuclear Research (NCBJ) estimated the key parameters for 1,305 heavy and super-heavy nuclei in the atomic number Z from 98 to 126 (and therefore also for elements still undiscovered) and for the number of neutrons N from 134 to 192.
“For our calculations, we used a multidimensional microscopic-macroscopic model that allows us to determine the binding energy of atomic nuclei” – explains Dr. Piotr Jachimowicz from the University of Zielona Góra. “For basic states and the so-called saddle points, we have determined such parameters as: nuclear masses, macroscopic energies, shell corrections and nuclear deformations – that is, the shapes of the nuclei in the ground state and in the saddle point. From them we deduced the energies of alpha decay between the ground states, the energies of the separation of one and two nucleons and the static, adiabatic heights of the fission barriers. ”
“Systematic calculations for odd nuclei, especially their cleavage barriers, are very rare – our work fills this gap” – adds Prof. Michał Kowal, Head of the NCBJ Theoretical Physics Department. “For systems with an odd number of protons, neutrons or both, we used the standard blocking BCS method. We could find the ground-state shapes and energies by minimizing seven axially symmetric strains. We searched for saddle points using the so-called “sinking” in three consecutive stages, using multidimensional deformation spaces, which involved the need to generate giant networks simulating various nuclear shapes. For this purpose, we used our supercomputer in the IT Center in Świerk for the calculations. ”
Some of the results obtained by the researchers concern parameters already known in the experiment and agree very well with these data. This confirms the correctness of the analysis carried out and allows us to believe that the determined values of previously unknown parameters are reliable.
The researchers emphasize that they managed to create one of the most complete data sets available “on the market”, necessary for the analysis of cross sections, i.e. the production probabilities of super-heavy nuclei in individual synthesis channels. “The accuracy of reproducing the masses and other values determined in the area analysed by us is one of the best existing estimates” – adds Prof. Janusz Skalski. “Our use of five- and seven-dimensional deformation spaces represents a significant improvement over other calculations performed so far. Our analysis is also one of the few that takes into account the odd nucleus, usually overlooked due to the difficulty of treating the odd nucleon.”
It is no coincidence that the results will go to the annals of Atomic Data and Nuclear Data Tables. Their importance is not limited to experiments aimed at creating new nuclides. “We have determined parameters, the knowledge of which may also be important for other areas of research” – explains Dr. Michał Kowal. “Among other things, we determined properties for the actinide nuclei, important from the point of view of reactor physics. Parameters determined and given in the paper can be used in astrophysical analyses and predictions concerning nucleosynthesis at particular stages of the universe’s evolution.”
P. Jachimowicz, M. Kowal, J. Skalski
Properties of heaviest nuclei with 98 ≤ Z ≤ 126 and 134 ≤ N ≤ 192,
Atomic Data and Nuclear Data Tables
(Available online 19 December 2020, 101393, in press).
https://doi.org/10.1016/j.adt.2020.101393
Until February 7, 2020, the work is available online at https://authors.elsevier.com/a/1cGMz,26poewBO; later it will be available in print and for journal subscribers only.
