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We have measured proton and ␣-particle branching ratios of states formed using the 19 F͑ 3 He, t͒ 19 Ne * reaction at a beam energy of 25 MeV. These ratios have a large impact on the astrophysical reaction rates of 15 O͑␣ , ␥͒ 19 Ne, 18 F͑p , ␥͒ 19 Ne, and 18 F͑p , ␣͒ 15 O, which are of interest in understanding energy generation in x-ray bursts and in interpreting anticipated ␥-ray observations of novae. We detected decay protons and ␣ particles using a silicon detector array in coincidence with tritons measured in the focal plane detector of our Enge split-pole spectrograph. The silicon array consists of five strip detectors of the type used in the Louvain-Edinburgh Detector Array, subtending angles from 130°to 165°with Ϸ14% lab efficiency. The correlation angular distributions give additional confidence in some prior spin-parity assignments that were based on ␥ branchings. We measure ⌫ p / ⌫ = 0.387± 0.016 for the 665 keV proton resonance, which agrees well with the direct measurement of Bardayan et al.

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The structure of the neutron-rich carbon isotopes 16,17,19 C has been investigated using one-neutron knockout reactions on a 9 Be target at approximately 60 MeV/nucleon. Partial cross sections and associated momentum distributions corresponding to final states of the 15,16,18 C residues were measured and compared with predictions based on a shell-model theory and an eikonal model of the reaction mechanism. Spectroscopic factors and l-value assignments are given. The ground-state spins of 17,19 C are ϩ , respectively. It is suggested that the accepted one-neutron separation energy for the ground state of 19 C needs to be revised upwards.

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In this Letter, we reported a study of the Snð; tÞ reaction at 40 MeV, on the seven stable, even Sn isotopes, to study the pattern of 11=2 À and 7=2 þ single-particle states as the neutron excess changes. The interpretation of the data relied only on the relative cross sections for these 14 transitions. The absolute cross sections given in Table I, columns 2 and 3, have now been found to be in error. This error has no impact on the rest of the paper, which utilized only the relative values of the cross sections. A numerical error in a measured quantity should, however, be corrected.In the experiment, the cross sections were normalized to the yield for elastic scattering in a monitor detector placed at 9.1 . The collimator in front of the detector had a diameter of 1 mm. In the analysis, it was mistakenly assumed to have had a 1-mm radius.The problem came to light in a recent experiment where the same reaction was studied at 37.5 MeV and significantly different cross sections were found [1], lower by a factor of $3:7 if corrected for a small energy dependence, than those in the Letter. This factor is reasonably constant, showing a rms variation of 8.6% among the 14 transitions. This fluctuation is consistent with the estimated uncertainties from other sources.In all subsequent experiments by our group, utilizing the spectrograph at the Yale tandem facility (e.g., Ref.[2]), a different technique for determining the absolute cross sections was used, a method that did not depend on a monitor at small angles. Instead, the target thicknesses were calibrated by measuring scattering at low bombarding energies and at larger scattering angles. This calibration was done directly with the spectrograph, using the same aperture as in the rest of the measurements. Therefore, the mistake reported here has no effect on the results reported from our subsequent measurements at Yale. *schiffer@anl.gov [1] A. J. Mitchell, Ph.D. thesis, University of Manchester, 2012; the data will be submitted to XUNDL, http://www.nndc.bnl.gov/ xundl/. [2] J. P. Schiffer et al., Phys. Rev. Lett. 108, 022501 (2012).