The 10B + 10B nuclear reactions and structure of light atomic nuclei

Jelavić Malenica, Deša (2015) The 10B + 10B nuclear reactions and structure of light atomic nuclei. Doctoral thesis, Faculty of Science > Department of Physics.

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Abstract

A rich variety of nuclear structures occur in light nuclei, in the vicinity of the A = 10 region, at similar excitation energies: from shell-model states to very exotic ones, e.g. molecular states with multiple valence nucleons or Bose-Einstein condensate states. Experimental data for this region is incomplete and often controversial. In order to study the structure of nuclei in this mass region, ^10B + ^10B reactions were measured at beam energies of 50 and 72.2 MeV. Reaction products were detected using a detector setup that consisted of four ΔE-E silicon detector telescopes, covering a large solid angle and allowing for the detection of single events as well as two- and three-particle coincidences. The selectivity of this reaction for populating different excited states was studied, together with a sequential decay of states in question. The complex structure of the low-lying states of the ^10B nucleus, which can be described as a mixture of shell model and cluster configurations of the type ^6Li_gs + α or ^6Li(0^+_2 , 1) + α, together with a high spin of the ground state J^π = 3+, enables this reaction to populate a range of different high-spin states at high excitation energies. The theories predicting an existence of exotic structures of the A = 10 nuclei can model many of these states, while some of the states are yet to be studied using new theoretical models. One nucleon transfer reactions populated a few well defined high excitation energy states of the ^11B and the ^11C. Some of these states were populated in a one nucleon transfer reaction for the first time. In the excitation energy spectra for the^ 9B and the ^9Be the first excited states, characterized as highly clustered structures, are missing. On the other hand, states that nicely fit into rotational bands of first excited states of these nuclei are clearly observed as their 9/2− members. Two nucleon transfer reactions strongly populated the ^8Be + ^12C channel. A coincident detection of three α-particles provided the information necessary to reconstruct the details of the ^10B + ^10B→5α reaction. That exotic reaction proceeds not only through the Hoyle state of the ^12C, but also through a rarely mentioned ^12C state at E_x = 24.4 MeV, whose parity and spin of are still unknown. In the three particle channel ^10B + d + 8Be a seldom observed high energy state in ^12C (E_x = 30.33 MeV) that decays through an exotic channel ^10B + d was populated. Excitation energy spectra of ^13C show a high selectivity in the three nucleon transfer channel. An α-transfer into states of the ^14N is very strong, as well as ^6Li transfer reaction to the states of the ^16O. A very strong α-decaying state is seen at the E_x = 18.9 MeV in the ^13C. Excited states of the ^14N at 13.2 and 15.39 MeV of excitation energy fit nicely to a recent AMD calculations as the head and the 5+ state of the ^10B(3+) + α rotational band (K^π = 3+). For the needs of this theses a novel calibration method was developed. It was implemented in a set of tools that allow an easy and accurate calibration of DSSSD detectors.

Item Type: Thesis (Doctoral thesis)
Keywords: nuclear reactions, light atomic nuclei, cluster states, DSSSD detectors
Supervisor: Milin, Matko
Date: 7 July 2015
Number of Pages: 126
Subjects: NATURAL SCIENCES > Physics > Nuclear Physics
Divisions: Faculty of Science > Department of Physics
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 13 Jul 2015 13:20
Last Modified: 13 Jul 2015 13:20
URI: http://digre.pmf.unizg.hr/id/eprint/4121

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