Nuclear reactions 10B+12C and the structure of light atomic nuclei

Abstract

U ovom se radu proučavaju nuklearne reakcije ulaznog kanala 10B+12C s ciljem istraživanja građe lakih atomskih jezgara oko nukleonskog broja A=10. Za jezgre iz tog masenog područja, poznata su mnoga stanja na bliskim energijama, koja se ne mogu opisati unutar istog modela. U ovom se radu stoga opisuju razni modeli, od običnog modela ljusaka do egzotičnih modela nuklearnih molekula i Bose-Einsteinovih kondenzata. S ciljem pronalaženja novih takvih stanja, izabrana je jezgra 10B kao projektil, s obzirom da su već njena niskoležeća stanja kombinacija modela ljusaka i klasterskih konfiguracija, a spin osnovnog stanja, iznimno je visok i iznosi Jπ =3+. Mjerenja su provedena na energiji snopa od 50 MeV-a, dok su produkti reakcije bilježeni sustavom od četiri ΔE-E silicijska detektora velikog prostornog kuta, koji omogućavaju mjerenja jednostrukih događaja, ali i dvo- i tročestičnih koincidencija. Analiza jednostrukih događaja, omogućila je rekonstrukciju spektara jezgri 12C, 13N, 15N, 15O i 16O, dok su iz dvočestičnih koincidencija rekonstruirani spektri 8Be i 14N. Na temelju tih spektara i recentnih eksperimentalnih i teorijskih radova, diskutirana je selektivnost pobuđivanja pojedinih stanja i struktura samih jezgara na koju ona ukazuju.In this work we study the nuclear reactions 10B+12C, with the goal of exploring the structure of light atomic nuclei around the nucleon number A=10. It is well known that those nuclei have many energy levels which are very close yet their structure and properties cannot be modeled in the same framework. For this reason we describe several different models, ranging from a simple Shell Model to several exotic ones, including the Nuclear Molecule model and the Bose-Einstein Condensate model. With the goal of finding states which correspond to these models, we have chosen the nucleus 10B as the projectile, because its low-lying states already have a mixture of shell model and cluster configurations and the spin of its ground state is extremely high, namely Jπ =3+. The projectile energy used was 50 MeV, while the detector system was made from four ΔE-E silicon detectors, covering a very wide solid angle. Both single-particle and multi-particle detection was possible. From the single particle detection, we have reconstructed the spectra of the following nuclei 12C, 13N, 15N, 15O and 16O, while the two particle detection was used to reconstruct the spectra of 8Be and 14N. A discussion on the selective activation of energy states and the corresponding structure of the nuclei is performed, based on the reconstructed spectra and the recent theoretical and experimental work in the field