The Al-26(. rho. ,. gamma. )Si-27 reaction: Stellar origins of galactic Al-26
To explain the Mg-26 isotopic anomaly seen in meteorites (Al-26 daughter) as well as the observation of 1809-keV gamma rays in the interstellar medium (live decay of Al-26) one must know, among other things the destruction rate of Al-26. Properties of states in Si-27 just above the Al-27 + p mass were investigated to determine the destruction rate of Al-26 via the Al-26(rho, gamma)Si-27 reaction at astrophysical temperatures. Twenty micrograms of Al-26 were used to produce two types of Al2O3 targets by evaporation of the oxide. One was onto a thick platinum backing suitable for (rho, gamma) work, and the other onto a thin carbon foil for the (He-3, d) reaction. The Al-26(rho, gamma)Si-27 excitation function, obtained using a germanium detector and voltage-ramped target, confirmed known resonances and revealed new ones at 770, 847, 876, 917, and 928 keV. Possible resonances below the lowest observed on at E{sub p} = 286 keV were investigated using the Al-26(He-3, d)Si-27 proton-transfer reaction. States in Si-27 corresponding to 196 and 286 keV proton resonances were observed. A possible resonance at 130 keV (postulated in prior work) was shown to have a strength of omega gamma is less than 0.02 microe V. By arranging four large NaI detector as a 4 pi calorimeter, the 196-keV proton resonance, and one at 247 keV, were observed directly, having omega gamma = 55 + or - 9 and 10 + or - 5 microe V respectively. Large uncertainties in the reaction rate have been reduced. At novae temperatures, the rate is about 100 times faster than that used in recent model calculations, casting some doubt on novae production of galactic Al-26.
- Research Organization:
- California Inst. of Tech., Pasadena, CA (USA)
- OSTI ID:
- 7059741
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALUMINIUM 26
ALUMINIUM ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CHARGED-PARTICLE REACTIONS
COSMIC DUST
DATA
DUSTS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXPERIMENTAL DATA
HADRON REACTIONS
INFORMATION
ISOTOPES
LIGHT NUCLEI
MESON REACTIONS
NUCLEAR REACTIONS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
RADIOISOTOPES
SECONDS LIVING RADIOISOTOPES
YEARS LIVING RADIOISOTOPES