Rotational excitation of the Hoyle state in 12C

Abstract

12C is synthesised in stars by fusion of three α particles. This process occurs through a resonance in the 12C nucleus, famously known as the Hoyle state. In this state, the 12C nucleus exists as a cluster of α particles. The state is the band-head for a rotational band with the 2+ rotational excitation predicted in the energy region 9 - 11 MeV. This rotational excitation can affect the triple-α process reaction rate by more than an order of magnitude at high temperatures (109 K). Depending on the energy of the resonance, the knowledge of the state can also help determine the structure of the Hoyle state. In the work presented here, the state of interest is populated by beta decay of radioactive 12N ion beam delivered by the IGISOL facility at JYFL, Jyväskylä.