The Hoyle state in 12 C

Abstract

The 7.65 MeV, J π =0 + , second excited state in 12 C is known as the Hoyle-state after Fred Hoyle. In the 1950s Hoyle proposed the existence of the state in order to account for the stellar abundance of carbon. Aside from its key role in the synthesis of the elements it is believed to possess a rather unusual structure, where the dominant degrees of freedom are those of α-particle clusters rather than nucleons. An understanding of the properties of the Hoyle state, for example its radius and excitations, has been the focus of a major experimental activity. Similarly, unravelling precisely why a cluster state should arise at precisely the right energy to promote synthesis of carbon has been a central theoretical challenge. To a significant extent, the Hoyle-state has become a cornerstone for state-of-the-art nuclear theory. This review examines the present status of both theory and experiment and indicates directions for future developments to resolve some of the remaining open questions.

αclusters and collective flow in ultrarelativistic carbon–heavy-nucleus collisions

“…The 12 C nucleus is of particular interest. It was described as a bound state of three elementary α−particles by Harrington [26] (for a review and further references see [27]). Numerous theoretical approaches were applied to its ground-state and excited states structure: the Bose-Einstein Condensation (BEC) model [28], the fermionic molecular dynamics (FMD) [29], antisymmetrized molecular dynamics [30], effective chiral field theory on the lattice [31], the no-core shell model [32,33], or the variational Green's function method (VMC) [34].…”

Enhancement of the Triple Alpha Rate in a Hot Dense Medium

“…Inserting the experimental value τ γ = 1.710 × 10 −13 sec [10,11], the values of the relevant constants, and expressing the energy as kinetic energy above threshold, one obtains…”

Three-body bremsstrahlung and the rotational character of theC12spectrum

“…The existence of such resonance was experimentally confirmed just a few years later [2]. Its properties have recently been thoroughly reviewed [3]. Since then, many other resonant states have been observed in 12 C [4][5][6][7][8][9].…”