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The main characteristics of nucleus–nucleus reactions with emission of high-energy particles are considered: the energy spectra, total cross section of their formation, and angular distributions. ...Correlations of high-energy particles with other reaction products are discussed. The possibilities of using the reactions with emission of high-energy particles for obtaining and studying the properties of cold exotic nuclei are discussed. The main theoretical approaches to explanation of the emission of high-energy particles in such reactions are described.
Direct Reactions in Heavy-Ion Collisions Bunakov, V. E.; Penionzhkevich, Yu. E.
Physics of particles and nuclei letters,
04/2023, Letnik:
20, Številka:
2
Journal Article
Recenzirano
It is shown that all the features of fast alpha particles with energies close to the two-body kinematic limit emerging in heavy-ion collisions are well explained by the direct theory of stripping and ...knock-on reactions. Recently found particles with energies exceeding this limit are interpreted as a result of the newly discovered reaction process, namely, the direct quasi-fission reaction.
MULTI-2, a 4π spectrometer for total reaction cross section measurements Siváček, I.; Penionzhkevich, Yu.E.; Sobolev, Yu.G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2020, Letnik:
976
Journal Article
Recenzirano
A detection setup for the direct measurement of the total reaction cross section with exotic nuclei is presented. The setup consists of a multi-detector telescope for beam-particle identification and ...a 4π gamma-ray spectrometer for the detection of prompt photons and neutrons accompanying the nuclear reactions. Measurements are based on the modified transmission method and gamma-ray tagging of nuclear reaction events. Registration efficiency and response characteristics of the gamma-ray spectrometer are investigated by Monte Carlo simulations and measurement with 60Co spectroscopic source. Results show strong a dependence of the registration efficiency on gamma-ray multiplicity, with minimum registration efficiency value of 70%. Evaluation of the registration efficiency for data measured in the total reaction cross section experiments is discussed.
Reactions involving loosely bound nuclei have many special features. An enhancement of interaction cross sections in the subbarrier energy region is one of them. This effect is pronounced for nuclei ...that have a cluster structure. Transfer and complete-fusion reactions are dominant interaction channels for them. Experimental data on the cross sections for fusion reactions induced by such nuclei deviate strongly from the predictions of the statistical compound-nucleus model at energies in the vicinity of the Coulomb barrier. Also, the cross sections for neutron transfer from
3,6,8
He and deuteron transfer from
6,9
Li were found to grow at deep subbarrier energies. These results are discussed from the point of view of the effect of the cluster structure of nuclei on the probability for their interaction at energies in the vicinity of the Coulomb barrier. A theoretical analysis of relevant experimental data was performed with allowance for the effect of outer neutrons and clusters in loosely bound nuclei of bombarding particles. The results of the present study may be used to solve some problems of astrophysics—in particular, to obtain deeper insight into the mechanism of the production of light elements in the Universe.
The energy spectra of alpha particles from reactions induced by 280-MeV
Ca beams incident to
Ta,
Au, and
U targets were measured at an angle of 0
by means of a high-resolution magnetic analyzer (MAVR ...setup). The sensitivity of the procedure used made it possible to measure alpha-particle yields that are five to six orders of magnitude less than the maximum yield. The cross section for the formation of alpha particles is shown to be dependent on their binding energy in the target nucleus. The experimental data obtained from these measurements were analyzed on the basis of the model of two- and three-body reaction channels and the model of moving sources.
This article is devoted to the description of the properties of the lightest nuclei with a large excess of neutrons. Light nuclei have always attracted attention due to the wide variety of their ...properties. While the structural characteristics of medium and heavy nuclei vary fairly smoothly, only single deviations are observed, the structure of light nuclei varies sharply, two neighboring light nuclei are often completely different from each other. This, on the one hand, makes their study a very interesting task, and on the other hand it makes it difficult to identify common trends. Our interest in light neutron-rich nuclei is connected with the desire to observe the characteristic features of nuclei overloaded with neutrons.
Two experiments made with the MSP144 stepped pole magnetic spectrometer of FLNR-JINR Dubna measured the energy spectra of α particles emitted at zero degree (collinear kinematic) in the reactions ...40Ar(220 MeV) + 232Th and 48Ca(270 MeV) + 238U. The study was pursued up to the maximum energy the alpha particles may have in a two-body reaction, without excitation of the reaction partners, the so-called kinematic limit. The observed cross sections in the vicinity of the kinematic limits were of the order of μb. In the indicated reactions, the heavy partners of the recorded alpha particles in the exit channel were respectively 268Sg and 282Db. At the kinematic limit, the heavy partners have excitation energies close to zero, therefore a high probability to survive.
One of the most complicated problems of experimental nuclear physics is the synthesis of exotic nuclei near the boundaries of stability. These nuclei, as a rule, are 10 or more neutrons away from ...stable nuclei, have a short lifetime (less than 1 ms) and low binding energy. All this determines special requirements to the choice of reactions for the synthesis of such nuclei and the method of their transportation and registration. Mainly, for the synthesis of exotic nuclei, reactions of fragmentation of the bombarding heavy ion, direct reactions of the types (p, d) , (d, p) , (d, n) , ( d , 3 He), etc., as well as reactions of fission and deep inelastic transfer are used.
The energy spectra of alpha particles emitted at an angle of 0
in the interaction of 400-MeV
Fe ions with
U,
Ta, and
Be targets were measured by means of a high-resolution magnetic analyzer (MAVR, ...which is the acronym of the Russian name of this setup). The energy spectra of charged particles ranging from Li to Ne were also measured. The experimental data obtained in this way indicate that the emission of alpha particles is a dominant process in the above reactions. Particles of high energy, up to those in the vicinity of the so-called kinematical limit for two-body reactions, were observed with a rather high yield. The sensitivity of the experimental procedure that employed the aforementioned magnetic analyzer made it possible to observe events characterized by cross-section values smaller by six to eight orders of magnitude than that at the maximum of the spectrum. The cross section for the production of light particles is shown to be dependent on their binding energy in the target. The experimental data obtained in this study were analyzed with aid of the moving-source model.
Nuclei in Astrophysics Penionzhkevich, Yu. E.
Journal of physics. Conference series,
06/2016, Letnik:
724, Številka:
1
Journal Article
Recenzirano
Odprti dostop
This work is an attempt to present some problems on the evolution of the Universe: the nucleosynthesis and cosmochronology from the standpoint of physics of particles and nuclei, in particular with ...the use of the latest results, obtained by means of radioactive nuclear beams. The comparison is made between the processes taking place in the Universe and the mechanisms of formation and decay of nuclei, as well as of their interaction at different energies. Examples are given to show the capabilities of nuclearphysics methods for studying cosmic objects and properties of the Universe. The results of investigations in nuclear reactions, induced by radioactive nuclear beams, make it possible to analyze the nucleosynthesis scenario in the region of light elements in a new manner.
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