EFFECT OF HIGH-ENERGY RESONANCES ON THE {sup 18}O(p, {alpha}){sup 15}N REACTION RATE AT AGB AND POST-AGB RELEVANT TEMPERATURES
- INFN-Laboratori Nazionali del Sud and University of Catania, I-95123 Catania (Italy)
The {sup 18}O(p, {alpha}){sup 15}N reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as {sup 19}F, {sup 18}O, and {sup 15}N. Fluorine is synthesized in the intershell region of asymptotic giant branch (AGB) stars, together with s-elements, by {alpha} radiative capture on {sup 15}N, which in turn is produced in the {sup 18}O proton-induced destruction. Peculiar {sup 18}O abundances are observed in R-Coronae Borealis stars, having {sup 16}O/{sup 18}O {approx}< 1, hundreds of times smaller than the galactic value. Finally, there is no definite explanation of the {sup 14}N/{sup 15}N ratio in pre-solar grains formed in the outer layers of AGB stars. Again, such an isotopic ratio is influenced by the {sup 18}O(p, {alpha}){sup 15}N reaction. In this work, a high accuracy {sup 18}O(p, {alpha}){sup 15}N reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. Indeed, current determinations are uncertain because of the poor knowledge of the resonance parameters of key levels of {sup 19}F. In particular, we have focused on the study of the broad 660 keV 1/2{sup +} resonance corresponding to the 8.65 MeV level of {sup 19}F. Since {Gamma} {approx} 100-300 keV, it determines the low-energy tail of the resonant contribution to the cross section and dominates the cross section at higher energies. Here, we provide a reaction rate that is a factor of two larger above T {approx} 0.5 10{sup 9} K based on our new improved determination of its resonance parameters, which could strongly influence present-day astrophysical model predictions.
- OSTI ID:
- 21471239
- Journal Information:
- Astrophysical Journal, Vol. 723, Issue 2; Other Information: DOI: 10.1088/0004-637X/723/2/1512; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
ALPHA PARTICLES
ASTROPHYSICS
CROSS SECTIONS
FLUORINE 19
ISOTOPE RATIO
KEV RANGE 10-100
MEV RANGE 01-10
NITROGEN 14
NITROGEN 15
NUCLEOSYNTHESIS
OXYGEN 16
OXYGEN 18
OXYGEN 18 TARGET
PROTON REACTIONS
REACTION KINETICS
STARS
TEMPERATURE DEPENDENCE
BARYON REACTIONS
CHARGED PARTICLES
CHARGED-PARTICLE REACTIONS
DIMENSIONLESS NUMBERS
ENERGY RANGE
EVEN-EVEN NUCLEI
FLUORINE ISOTOPES
HADRON REACTIONS
IONIZING RADIATIONS
ISOTOPES
KEV RANGE
KINETICS
LIGHT NUCLEI
MEV RANGE
NITROGEN ISOTOPES
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
OXYGEN ISOTOPES
PHYSICS
RADIATIONS
STABLE ISOTOPES
SYNTHESIS
TARGETS