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The results presented in this thesis are based on the analysis of the S1620 experiment performed at TRIUMF, where multi-nucleon and cluster transfer reactions of the 9^Li beam of 74.8 MeV on the ≈ 1 mg/cm2 LiF target were used to populate excited states of neutron-rich light nuclei 10^Be, 12^Be and 13^B. The main motivation behind this work was the need for experimental data to wage on the existence of molecular-like structures in the excited states of these nuclei and to resolve inconsistent observations from the previous measurements. For the latter two nuclei, the use of transfer reactions and resonant particle spectroscopy method to study molecular structures is independent and novel approach to more commonly used resonant elastic scattering and inelastic breakup measurements. Most important results are the first experimental observation of the decays of the 12^Be excited states to the 6^He+6^He* (1.8 MeV, 2^+) channel and the 13^B decays to the 10^Be+3^H and 7^Li+6^He channels. In the 10^Be nucleus, new states were observed in the 8^Be+nn decay channel and past results for the 4^He+6^He* (1.8 MeV, 2^+) channel were confirmed, alongside newly observed states. In both cases only one previous measurement was available. New states were observed in the 4^He+6^He, 4,6^He+8,6^He and 9^Li+4^He decay channels of the 10^Be, 12^Be and 13^B nuclei, respectively. Even though branching ratios were not determined, due to limited resolution of the present data, important spectroscopic information on the cluster structures in these nuclei was obtained, which could be related to the molecular α-Xn- α and α-2n-t-α structure of the 10,12^Be and 13^B nuclei, respectively. Rad ne sadrži sažetak na drugom jeziku.

U okviru rada identificirani su karakteristični elektromagnetski prijelazi jezgara olova 205-210^Pb proizvedeni nuklearnom reakcijom 40^Ar+208^Pb mjerenom magnetskim spektrometrom PRISMA u koincidenciji s detektorom gama-zračenja CLARA na akceleratorskom postrojenju INFN - LNL, Italija. U spektrima pobuđenja izotopa olova izazvanih reakcijom prijenosa neutrona opažena su snažna pobuđenja jednočestičnih stanja kao i kolektivnih stanja od kojih je najznačajnije 3^- stanje izotopa 208Pb. Stanje 3^- igra važnu ulogu u spektrima pobuđenja susjednih jezgara. Opažena su i pobuđenja koja se mogu opisati vezanjem kolektivnih i jednočestičnih stanja. Jakosti elektromagnetskih prijelaza korištene su za izvrednjavanje udarnih presjeka pobuđenih stanja te evaluaciju udarnog presjeka osnovnog stanja usporedbom podataka mjerenja fragmenata i fragmenata u koincidenciji s γ- zračenjem. Dobiveni rezultati uspoređeni su s kodom GRAZING. Takav postupak nam je pomogao u evaluaciji udarnog presjeka u drugim mjerenjima, posebno onih koji koriste (manje intenzivne) radioaktivne snopove. Pokazalo se da su reakcije prijenosa nukleona pogodne za proizvodnju neutronski bogatih teških jezgara kada se koriste neutronski bogati snopovi kao laki partneri u reakciji. Within the work, characteristic electromagnetic transitions of 205-210Pb isotopes, produced in the 40^Ar + 208^Pb nuclear reaction, were identified. The reaction was measured by a magnetic spectrometer PRISMA coupled to the CLARA gamma-ray detector at the INFN-LNL accelerator complex, Legnaro, Italy. In the neutron transfer channels, strong excitations of single-particle states as well as collective states were observed, the most significant of which was the 3^- state in 208^Pb. The 3^- state plays an important role in the excitation spectra of neighboring nuclei. Excitations of states with the structure that can be described as a coupling of collective and single-particle states have also been observed. The intensities of electromagnetic transitions were used to evaluate cross sections of the ground state by comparing the data where only fragments, with the data where fragments in coincidence with gamma radiation were detected. The obtained results were compared with the code GRAZING. Such a procedure helped us to evaluate cross sections of ground state in other measurements, especially those using (less intensive) radioactive beams. Multinucleon transfer reactions have been shown to be suitable for the production of neutron-rich heavy nuclei when neutron-rich beams are used as light partners in the reaction.

U ovom radu predstavljeni su rezultati proučavanja reakcija prijenosa nukleona u sustavu 94Rb + 208Pb na energiji oko Coulombove barijere. Osnovni cilj ovog rada bio je proučiti mogućnost upotrebe reakcija prijenosa nukleona za proizvodnju i pobuđenje neutronski bogatih teških jezgara oko jezgre 208Pb, posebno jezgara koje se na karti nuklida nalaze lijevo i ispod jezgre 208Pb. Produkti reakcije 94Rb + 208Pb detektirani su γ- spektrometrom Miniball u kombinaciji s čestičnim CD detektorom. Radioaktivni snop 94Rb ubrzan je akceleratorskim kompleksom ISOLDE na CERNu. U radu su identificirani elektromagnetski prijelazi vezani uz produkte nuklearne reakcije, gdje su različiti izotopi prepoznati pomoću poznatih elektromagnetskih prijelaza. Uz pomoć tabličnih vrijednosti energija γ zraka i njihovih intenziteta, izmjereni prijelazi pridruženi su izotopima nastalim reakcijom prijenosa nukleona, izotopima vezanim uz pozadinsko zračenje, ili izotopima koji pripadaju lancu raspada radioaktivnog snopa 94Rb. U mjerenjima pod snopom, većina opaženih elektromagnetskih prijelaza vezana je uz kratkoživuće izotope 94Sr i 93Sr. U mjerenjima u kojima je meta bila ozračena snopom, a nakon što je sam snop bio isključen, identificirani su elektromagnetski prijelazi vezani uz stabilni 94Zr, te dugoživuće izotope 93Y i 93Zr. Opaženi su i prijelazi vezani uz izotope koje pridružujemo prirodnoj radioaktivnosti, kao npr. 214Po, 214Bi i dr. Nakon prepoznavanja elektromagnetskih prijelaza vezanih uz prirodnu radioaktivnost, te vezanih uz raspad radioaktivnog snopa 94Rb, identificirali su se i oni elektromagnetski prijelazi koji su rezultat pobuđenja jezgara snopa i mete, te reakcija prijenosa nukleona. Identificirano je niz elektromagnetskih prijelaza koji odgovaraju lakšem fragmentu reakcije: 92Rb, 93Rb, 95Rb i 94Sr, te težem fragmentu reakcije: 207Pb i 209Pb. Usporedbom intenziteta tih raspada i relativnog udarnog presjeka u svakom kanalu prijenosa, zaključeno je da je prijenos neutrona od Rb prema Pb (94Rb + 208Pb → 93Rb + 209Pb) značajno snažniji kanal od prijenosa neutrona iz Pb prema Rb (94Rb + 208Pb → 95Rb + 207Pb). Ovaj zaključak nam govori da se reakcije prijenosa nukleona na energijama oko Coulombove barijere uz upotrebu radioaktivnih snopova mogu koristiti kao mehanizam dobivanja neutronski bogatih teških jezgri. Dodatna analiza trostrukih koincidencija, fragmenat-γ-γ, pomoći će u preciznijem uspoređivanju kaskada raspada i u razlučivanju mehanizma reakcije. Usporedba s nuklearnim modelima omogućit će preciznije određivanje ukupnog udarnog presjeka u različitim kanalima prijenosa nukleona. This work presents selected results of the analysis of nucleon transfer reactions in the 94Rb + 208Pb system at energy close to the Coulomb barrier. The main goal of this study was to investigate the ability of the nucleon transfer reactions in the production of heavy neutron-rich nuclei in the vicinity of 208Pb, in particular in the region of the nuclear chart east and south of 208Pb. The reaction products of 94Rb + 208Pb have been detected by the Miniball γ-spectrometer coupled to the particle CD detector. The radioactive beam 94Rb was accelerated by the ISOLDE accelerator complex at CERN. Using known energies and intensities of γ -rays, measured electromagnetic transitions have been associated with the isotopes produced in the nucleon transfer reaction, the isotopes produced by the decay of the radioactive 94Rb beam, and associated with the natural radiation. The strongest electromagnetic transitions observed while the beam was impinging on the target belong to the short-lived isotopes 94Sr and 93Sr. In the spectra detected when the beam was switched off, the dominant transitions are associated with the stable 94Zr, and long-lived 93Y and 93Zr isotopes. Strong transitions in isotopes related to the natural radioactivity, such as 214Po, 214Bi have also been observed. After the electromagnetic transitions related to natural radioactivity and the decay of the 94Rb isotopes have been identifed, the electromagnetic transitions resulting from the excitation of the beam-like and target-like nuclei were established. They correspond to the light reaction fragment: 92Rb, 93Rb, 95Rb and 94Sr, and to the heavy reaction fragment: 207Pb and 209Pb. By comparing the intensity of these decays and relative cross sections in each transfer channel, it was concluded that the neutron transfer from Rb to Pb (94Rb + 208Pb → 93Rb + 209Pb) was much stronger than the transfer of neutrons from Pb to Rb (94Rb + 208Pb → 95Rb + 207Pb). Such a conclusion strongly supports the use of the nucleon transfer reactions at energies close to the Coulomb barrier using radioactive beams for the production of the heavy neutron-rich nuclei. An additional analysis of triple coincidences, fragment-γ-γ, will help to define more accurately the deexcitation of nuclei and to gather further information about the reaction mechanism. Comparison with nuclear models will allow a more precise determination of the total cross section in different nucleon transfer channels.