Temperature and Density Conditions for Alpha Clustering in Excited Self-Conjugate Nuclei

Starting from experimental studies on alpha-clustering in excited self-conjugate nuclei (from O-16 to Si-28), temperature and density conditions for such a clustering are determined. Measured temperatures have been found in the range of 5.5-6.0 MeV, whereas density values of 0.3-0.4 times the saturation density are deduced, i.e., 0.046 to 0.062 fm(-3). Such a density domain is also predicted by constrained self-consistent mean field calculations. These results constitute a benchmark for alpha clustering from self-conjugate nuclei in relation to descriptions of stellar evolution and supernovae.