| Abstract | Lake atomske jezgre u okolici A = 10 pokazuju vrlo različite strukture na bliskim energijama pobuđenja, od ljuskastih do sasvim egzotičnih, kao što su molekulska stanja s više valentnih nukleona, ili Bose-Einsteinovi kondenzati. Eksperimentalni podaci u tom području nepotpuni su i često kontroverzni. S ciljem proučavanja jezgri iz tog masenog područja, nuklearne reakcije 10B + 10B mjerene su na dvije energije snopa = 50 i 72.2 MeV. Produkti reakcija bilježeni su detektorskim sustavom sastavljenim od četiri silicijska ΔE-E teleskopa, koji je pokrivao veliki prostorni kut i omogućavao mjerenje jednostrukih događaja, te dvo- i tročestičnih koincidencija. Proučavana je selektivnost pobuđivanja pojedinih stanja, te njihov sekvencijalni raspad. U skladu sa složenom strukturom jezgre 10B, čija su niskoležeća stanja mješavina ljuskastih (jednočestičnih) i klasterskih konfiguracija tipa 6Ligs + α ili 6Li(0+2 , 1) + α, te visoki spin osnovnog stanja jezgre 10B (Jπ = 3+), pobuđen je čitav niz stanja na visokim energijama pobuđenja, vjerojatno visokog spina, od kojih se mnoga uklapaju u modele koji predviđaju neobične klasterske strukture tih jezgara, a neka tek ugrađuju u novije teorijske modele. Mehanizmom prijenosa neutrona, odnosno protona, vrlo je jako pobuđeno nekoliko stanja u jezgrama 11B i 11C, na visokim energijama pobuđenja, za koja dosad nije zabilježeno pobuđivanje prijenosom jednog nukleona. U spektrima pobuđenja 9Be i 9B nedostaje prvo pobuđeno stanje izrazito klasterske građe, no s druge strane javljaju se stanja koja se vrlo lijepo uklapaju u rotacijske vrpce osnovnih stanja tih jezgra, kao članovi 9/2−. Prijenosom dva nukleona intenzivno je pobuđen kanal 8Be + 12C. Detekcija tri α- čestice nastale kroz ovaj kanal omogućila je rekonstrukciju detalja procesa 10B + 10B → 5α, koji se odvija preko Hoyleovog stanja u jezgri 12C, ali i rijetko isticanog stanja na Ex = 24.4 MeV, kojemu još nisu poznati spin i paritet. U tročestičnom izlaznom kanalu 10B + d + 8Be, pobuđeno je i rijetko viđeno stanje na visokoj energiji pobuđenja u 12C (na 30.33 MeV), koje se raspada kroz egzotični kanal 10B + d. Dobiveni spektri pokazuju veliku selektivnost pri prijenosu tri nukleona u stanja jezgre 13C, a jaki su i prijenosi α-čestice u pojedina stanja jezgre 14N, te 6Li u stanja jezgre 16O. Naročito je jako izraženo α-stanje na 18.9 MeV u 13C, te stanja 14N na 13.2 i 15.39 MeV, koja se uklapaju u vrlo nedavne AMD račune za jezgru 14N, kao glava i pobuđeno 5+ stanje rotacijske vrpce Kπ = 3+ bazirane na 10B(3+) + α strukturi. Još jedan rezultat ovog rada svakako je doprinos na području kalibracije DSSSD detektora, gdje je razvijena nova metoda i posebni programski paket prilagođen za njeno jednostavno korištenje. |
| Abstract (english) | 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 6Ligs + α or 6Li(0+2 , 1) + α, together with a high spin of the ground state Jπ = 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 Ex = 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 (Ex = 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 Ex = 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 (Kπ = 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. |
