Experimental determination of the {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reaction rates

Journal Article · Thu Mar 15 00:00:00 EDT 2007 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.75.035810· OSTI ID:20995177

Chafa, A; Ouichaoui, S ^[1]; Tatischeff, V; Coc, A; Garrido, F; Kiener, J; Lefebvre-Schuhl, A; Thibaud, J -P ^[2]; Aguer, P ^[3]; Barhoumi, S ^[4]; Hernanz, M ^[5]; Jose, J ^[6]; Sereville, N de ^[2]

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1. USTHB-Faculte de Physique, BP 32, El-Alia, 16111 Bab Ezzouar, Algiers (Algeria)
2. CSNSM, IN2P3-CNRS and Universite Paris-Sud, F-91405 Orsay Cedex (France)
3. CENBG, IN2P3-CNRS and Universite Bordeaux I, F-33175 Gradignan (France)
4. UMBM, B.P. 166, Route ICHBILLIA, 28000 M'sila (Algeria)
5. Institut de Ciencies de l'Espai (CSIC) and Institut d'Estudis Espacials de Catalunya, E-08034 Barcelona (Spain)
6. Departament de Fisica i Enginyeria Nuclear (UPC) and Institut d'Estudis Espacials de Catalunya, E-08034 Barcelona (Spain)

The {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reactions are of major importance to hydrogen-burning nucleosynthesis in a number of different stellar sites. In particular, {sup 17}O and {sup 18}F nucleosynthesis in classical novae is strongly dependent on the thermonuclear rates of these two reactions. The previously estimated rate for {sup 17}O(p,{alpha}){sup 14}N carries very large uncertainties in the temperature range of classical novae (T=0.01-0.4 GK), whereas a recent measurement has reduced the uncertainty of the {sup 17}O(p,{gamma}){sup 18}F rate. We report on the observation of a previously undiscovered resonance at E{sub c.m.}=183.3 keV in the {sup 17}O(p,{alpha}){sup 14}N reaction, with a measured resonance strength {omega}{gamma}{sub p{alpha}}=(1.6{+-}0.2)x10{sup -3} eV. We studied in the same experiment the {sup 17}O(p,{gamma}){sup 18}F reaction by an activation method, and the resonance strength was found to amount to {omega}{gamma}{sub p{gamma}}=(2.2{+-}0.4)x10{sup -6} eV. The excitation energy of the corresponding level in {sup 18}F was determined to be 5789.8{+-}0.3 keV in a Doppler shift attenuation method measurement, which yielded a value of {tau}<2.6 fs for the level lifetime. The {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reaction rates were calculated using the measured resonance properties and reconsidering some previous analyses of the contributions of other levels or processes. The {sup 17}O(p,{alpha}){sup 14}N rate is now well established below T=1.5 GK, with uncertainties reduced by orders of magnitude in the temperature range T=0.1-0.4 GK. The uncertainty in the {sup 17}O(p,{gamma}){sup 18}F rate is somewhat larger because of remaining obscurities in the knowledge of the direct capture process. These new resonance properties have important consequences for {sup 17}O nucleosynthesis and {gamma}-ray emission of classical novae.

• OSTI ID: 20995177
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 75, Issue 3; Other Information: DOI: 10.1103/PhysRevC.75.035810; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
DSA METHOD
EV RANGE
EXCITATION
FLUORINE 18
GAMMA RADIATION
HYDROGEN BURNING
KEV RANGE
NITROGEN 14
NOVAE
NUCLEOSYNTHESIS
OXYGEN 17 TARGET
PROTONS
REACTION KINETICS
RESONANCE
TEMPERATURE RANGE