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Reso»rice neutron interactions with the stable isotopes of magnesium were measured at the Oak Ridge electron linear accelerator time-of-flight facility. The transmission of a natural metal sample (78.7% Mg} was measured at 200 m and capture by natural metal and by enriched isotope samples was measured at 40 m. Twenty-six reso»races in Mg+ n up to 1.8 MeV were fitted with Breit-Wigner multilevel parameters. The data were sufficient to assign spin and parity to 19 of these. The capture data were analyzed for resonances up to 850 keV for Mg+n, 265 keV for 2 Mg+n (17+ resonances), and 440 keV for Mg+n (4 resonances). Average capture at stellar interior temperatures was calculated. The Mg+ n data serve to assess the isospin impurities in three isobaric analog states. Three other states exhibit reduced neutron widths each several percent of the Wigner limit which may be understood in terms of simple shell model configurations.

A best set of neutron-capture cross sections has been evaluated for the most important~-process isotopes. With this data base, -process studies have been carried out using the traditional model which assumes a steady neutron flux and an exponential distribution of neutron irradiations. The calculated aN-curve is~n excellent agreement with the empirical aN-values of pure~-process nuclei. Simultaneously, good agreement is found between the difference of solar and~-process abundances and the abundances of pure~-process nuclei. We also discuss the abundance pattern of the iron group elements where our~-process results complement the abundances obtained from explosive nuclear burning.

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Neutron capture cross sections are averaged over Maxwell -Boltzmann neutron distributions for temperatures pertinent to slow nucleosynthesis (s process) in red giant stars. Such cross sections, together with isotopic abundances, provide the major quantitative experimental tests of the theory.The cross sections are tabulated at convenient intervals from kÃ=5 keV to kT =90 keV where data are available. In many cases it has been possible to supplement the often fragmentary {as of June 1964) data with evidence from nuclear systematics.

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