C 13 («,a)C 13 cross sections at center-of-mass angles 54.7°, 107.9°, 142.6°, and 169.6° and C 13 (a,#)0 16 cross sections at 0° have been measured at a-particle energies from 2 to 3.5 MeV. From dispersion-theory analysis, a consistent set of J* and partial-width values has been obtained for eleven states of the compound nucleus O 17 with excitation energies between 8 and 9 MeV. I. INTRODUCTIONT HE C 13 (a,w)0 16 reaction has been extensively investigated 1-5 at a-particle bombarding energies below 5 MeV. Resonances from sharp energy states of the compound nucleus O 17 are observed. We have measured 6 the C 13 (a,a)C 13 differential elastic-scattering cross sections for a-particle bombarding energies from 2.0 to 3.5 MeV at center-of-mass angles 54.7, 107.9,142.6, and 169.6°. C ls (a,n)O u differential reaction cross sections at 0° were measured simultaneously. Elastic-scattering and reaction data were analyzed to determine the J T and the a-particle and neutron partial widths of the states of O 17 corresponding to the observed resonances.The range 2 to 3.5 MeV of a-particle bombarding energies corresponds to the range 7.9 to 9 MeV of excitation energies in the compound nucleus O 17 . Values of / and of neutron and a-particle partial widths for many of the states at these excitation energies were known from C 13 (a,w)0 16 differential cross sections 2-5 and from total cross sections of O 16 for neutrons. 2 -5 » 7 From interference terms in C 13 (a,w)0 16 angular distributions, 4 -5 relative parities of a number of states were known. To determine parities and to make complete determinations of J and partial-width values, C 13 -(a,a)C 13 and O u (n y n)O u elastic-scattering experiments are necessary. The parameters of two states at the low end of the energy interval have recently been determined from analysis of 0 16 (^,w)0 16 angular distributions. 8

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