3α-cluster structure of the0+states inC12

Abstract

The 0 + states of 12 C are considered within the framework of the microscopic three-α-cluster model. The main attention is paid to accurate calculation of the width of the extremely narrow near-threshold 0 + 2 state which plays a key role in stellar nucleosynthesis. It is shown that the

Momentum distributions of α particles from decaying low-lyingC12resonances

“…The low-lying resonance states of 12 C have been studied over many years both theoretically and experimentally, motivated partly by their astrophysical importance [1][2][3][4][5][6][7][8][9][10]. Surprisingly, many issues are still not really understood, e.g., the energies, angular momenta, structure, and decay properties of the resonances.…”

“…Decay through 8 Be(2 + ) is possible in both cases but this state is rather broad and the result would be hard to distinguish from direct decay. We see no indication of population of this channel in the numerical results.…”

“…They can decay via the energetically favorable 8 Be(0 + ), which asymptotically must be described by one of the adiabatic potentials with the 8 Be+α structure. The signature is simply that this potential approaches the complex energy of the 8 Be(0 + ) resonance.…”

“…First V i must reproduce the low-energy two-body scattering properties that can be obtained independently for each partial wave resulting in angular-momentum-dependent or nonlocal interactions. We rely on the experience gained previously especially through [18], and we choose an AliBodmer potential [25] slightly modified to reproduce the s-wave resonance of 8 Be. The phase shifts are essentially unchanged and reproduce α-α scattering data but to describe sequential decays properly the two-body subsystems must also have the correct energies.…”

“…We have performed a Monte Carlo integration over the phase space. The sequential decay, respectively, of 59, 15, and 4% through 8 Be(0 + ) is removed. Labels are as in Table I. must cover overlapping distributions deviating somewhat from the equilateral triangle and corresponding to similar but less symmetric configurations.…”