The Ne-Na Cycle and the ¹²C+α Reaction

Abstract

Some problems concerning the measurement of reaction rates involving charged particle reactions are indicated in Fig. 1. For a nondegenerate gas the energy distribution of the particles follows the Maxwell-Boltz-man law. The maximum of such a distribution is reached e.g. for T = 15 × 10⁶ °K at kT = 1.3 keV. For this reason a nuclear reaction relevant to stellar burning proceeds far below the Coulomb barrier and its energy dependence is hence controlled by the barrier penetrability. In folding those two functions one obtains the so-called Gamow peak (Fig. 1) whose integral represents the non-resonant reaction rate. The effective energy is higher than kT and amounts to e.g. E_eff =5.9 keV for the p+p reaction at T = 15 × 10⁶ °K. This is still much too low for any direct yield measurement using present techniques.