The $$^3$$He+$$^5$$He$$\rightarrow $$ $$\alpha $$+$$\alpha $$ reaction below the Coulomb barrier via the Trojan Horse Method

Abstract

For the first time in an application to nuclear astrophysics, a process induced by the unstable $$^5$$ He = ( $$^4$$ He-n) nucleus, the $$^3$$ He+ $$^5$$ He $$\rightarrow $$ 2 $$\alpha $$ reaction, has been studied through the Trojan Horse Method (THM). For that purpose, the quasi-free (QF) contribution of the $$^9$$ Be( $$^3$$ He, $$\alpha \alpha $$ ) $$^4$$ He reaction was selected at $$E_{^{3}\text{ He }}=4$$ MeV incident energy. The reaction was studied in a kinematically complete experiment following a recent publication (Spitaleri et al. in Eur Phys J A 56:18, 2020), where for the quasi free contribution the momentum distribution between $$\alpha $$ and $$^5$$ He particle cluster in the $$^9$$ Be nucleus in the ground state have been extracted. The angular distribution of the QF $$^3$$ He+ $$^5$$ He $$\rightarrow $$ 2 $$\alpha $$ reaction was measured at $$\theta _{cm}$$ = 78 $$^{\circ }$$ –115 $$^{\circ }$$ . The energy dependence of the differential cross section of the $$^3$$ He+ $$^5$$ He $$ \rightarrow $$ 2 $$\alpha $$ virtual reaction was extracted in the energy range $$E_{cm}$$ = 0–650 keV. The total cross section obtained from the Trojan-horse method was normalized to absolute cross sections from a theoretical calculation in the energy range $$E_{cm}$$ =300–620 keV.