Search

We conducted the coincidence measurement of α particles inelastically scattered from $^{20}$Ne at 0° and decay charged particles in order to search for the alpha-particle condensed state. We compared the measured excitation-energy spectrum and decay branching ratio with the statistical-decay-model calculations, and found that the newly observed states at Ex=23.6, 21.8, and 21.2 MeV in $^{20}$Ne are strongly coupled to a candidate for the 4α condensed state in $^{16}$O. This result presents the first strong evidence that these states are the candidates for the 5α condensed state.

The triple alpha reaction is one of the most important reactions in the nuclear astrophysics. However, its reaction rate in high temperature environments at T9> 2 was still uncertain. One of the major origins of the uncertainty was that the radiative-decay probability of the 31− state in $^{12}$C was unknown. In the present work, we have determined the radiative-decay probability of the 31− state to be 1.3−1.1+1.2×10−6 by measuring the $^{1}$H($^{12}$C,$^{12}$Cp) reaction for the first time, and derived the triple alpha reaction rate in high temperature environments from the measured radiative-decay probability. The present result suggests that the 31− state noticeably enhances the triple alpha reaction rate although the contribution from the 31− state had been assumed to be small.