Improved astrophysical rate for the O(p, ) N reaction by underground measurements
C.G. Bruno (SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom)
; M. Aliotta (SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom); P. Descouvemont (Physique Nucléaire Théorique et Physique Mathématique, Université Libre de Bruxelles (ULB), Brussels, Belgium); A. Best (Università di Napoli “Federico II”, INFN, Sezione di Napoli, Napoli, Italy); T. Davinson (SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom); et al - Show all 38 authors
The $^{18}$O(p,α)$^{15}$N reaction affects the synthesis of $^{15}$N, $^{18}$O and $^{19}$F isotopes, whose abundances can be used to probe the nucleosynthesis and mixing processes occurring deep inside asymptotic giant branch (AGB) stars. We performed a low-background direct measurement of the $^{18}$O(p,α)$^{15}$N reaction cross-section at the Laboratory for Underground Nuclear Astrophysics (LUNA) from center of mass energy keV down to keV, the lowest energy measured to date corresponding to a cross-section of less than 1 picobarn/sr. The strength of a key resonance at center of mass energy keV was found to be a factor of 10 higher than previously reported. A multi-channel R-matrix analysis of our and other data available in the literature was performed. Over a wide temperature range, GK, our new astrophysical rate is both more accurate and precise than recent evaluations. Stronger constraints can now be placed on the physical processes controlling nucleosynthesis in AGB stars with interesting consequences on the abundance of $^{18}$O in these stars and in stardust grains, specifically on the production sites of oxygen-rich Group II grains.