The excess of the energy of the excited atomic nucleus above the neutron biding energy could be given to giant resonances. These excitations are described macroscopically as nucleon vibrations in the nucleus. By measuring their decay, can be obtained the information about the properties of the atomic nuclei, in which giant resonances are excited. The well-known are giant dipole resonance (GDR), studied in the process of their g decay, in many experiments carried out in the last decades. In contrast to the GDR, the properties of giant quadrupole resonance (GQR) have not been extensively investigated. The g decay of GQR has been measured so far only in the experiment carried out in the 1980s, using inelastic scattering of ¹⁷O on ²⁰⁸Pb. The outcome of this experiment are the only published results of the GQR g decay studies.

Thanks to the construction of the experimental setup for nuclear physics research at the Bronowice Cyclotron Center (CCB) of the Institute of Nuclear Physics, Polish Academy of Sciences, a newly established center for hadron therapy, it has been started the research on GQR g decay using a high-energy proton beam. The article published in Phys. Rev. C shows the results of the measurement of GQR g decay for the ²⁰⁸Pb nucleus performed as one of the first nuclear physics experiments at the CCB. To excite giant resonances the inelastic scattering of protons with an energy of 85 MeV on a ²⁰⁸Pb target was used. During the experiment, the energy of scattered protons, carrying information about the excitation energy of ²⁰⁸Pb nuclei, and the energy of grays emitted as a result of the decay of excited states, were measured simultaneously. The data corresponding to the decay to the ground state, for which the excitation energy was equal to the energy of the emitted g rays, were analyzed. Taking into account the observed g decay of GDR, the spectrum of g rays emitted from the GQR decay was obtained. As the result of the analysis, the probability of GQR decay by the g ray emission was determined to be 3 × 10^-4. This value confirms the previous result obtained for the inelastic scattering of ¹⁷O ions.

Wasilewska, M. Kmiecik, M. Ciemała, A. Maj, F.C.L. Crespi, A. Bracco, M.N. Harakeh, P. Bednarczyk, S. Bottoni, S. Brambilla, F. Camera, I. Ciepał, N. Cieplicka-Oryńczak, M. Csatlos, B. Fornal, V. Gaudilla, J. Grębosz, J. Isaak, Ł.W. Iskra, M. Jeżabek, A.J. Krasznahorkay, S. Kihel, M. Krzysiek, P. Lasko, S. Leoni, M. Lewitowicz, J. Łukasik, M. Matejska-Minda, K. Mazurek, P.J. Napiorkowski, W. Parol, P. Pawłowski, L.Q. Qi, M. Saxena, Ch. Schmitt, Y. Sobolev, B. Sowicki, M. Stanoiu, A. Tamii, O. Wieland, M. Ziębliński

γ decay to the ground state from the excitations above the neutron threshold in the ²⁰⁸Pb(p,p′γ) reaction at 85 MeV

Phys. Rev. C 105, 014310 (2022)

DOI:10.1103/PhysRevC.105.014310

The Josephson effect is a quantum phenomenon appearing in superconductors.
It consists in the spontaneous flow of electric current, due to tunneling, between the two
superconductors separated by a thin insulator layer. The current flow is induced by
phase difference of wave functions describing superconducting electrons on both
sides of the insulator. This is called the Josephson junction.
The phenomenon occurs in metals as well as in ultracold atomic gases.
Search for the Josephson effect in nuclear systems
have been going on for almost half a century.
Theoretical analysis of recent experiments involving collisions of Nickel-60 and Tin-116
provided strong arguments for creation of the Josephson junction.
Contrary to the previous measurements where
the pair transfer cross section has been investigated, this time the gamma radiation spectrum
was analyzed. It turned out that the spectrum of emitted gamma rays agrees with the theoretical
predictions assuming the formation of the so-called AC Josephson junction.

Piotr Magierski

The Tiniest Superfluid Circuit in Nature

Physics 14, 27 (2021)

DOI:10.1103/Physics.14.27

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.