First experimental determination of the radiative-decay probability of the 31− state in 12C for estimating the triple alpha reaction rate in high temperature environments

Abstract The triple alpha reaction is one of the most important reactions in the nuclear astrophysics. However, its reaction rate in high temperature environments at T 9 > 2 was still uncertain. One of the major origins of the uncertainty was that the radiative-decay probability of the 3 1 − state in 12C was unknown. In the present work, we have determined the radiative-decay probability of the 3 1 − state to be 1.3 − 1.1 + 1.2 × 10 − 6 by measuring the 1H(12C,12Cp) 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 3 1 − state noticeably enhances the triple alpha reaction rate although the contribution from the 3 1 − state had been assumed to be small.