S. T. Marley

Democratic Decay of 6Be Exposed by Correlations

The interaction of an E/A=70-MeV (7)Be beam with a Be target was used to populate levels in (6)Be following neutron knockout reactions. The three-body decay of the ground and first excited states into the α+p+p exit channel were detected in the High Resolution Array. Precise three-body correlations extracted from the experimental data allowed us to obtain insight into the mechanism of the three-body democratic decay. The correlation data are in good agreement with a three-cluster-model calculation and thus validate this theoretical approach over a broad energy range.

Democratic Decay ofBe6Exposed by Correlations

The interaction of an E/A=70-MeV (7)Be beam with a Be target was used to populate levels in (6)Be following neutron knockout reactions. The three-body decay of the ground and first excited states into the α+p+p exit channel were detected in the High Resolution Array. Precise three-body correlations extracted from the experimental data allowed us to obtain insight into the mechanism of the three-body democratic decay. The correlation data are in good agreement with a three-cluster-model calculation and thus validate this theoretical approach over a broad energy range.

Fusion reactions with the one-neutron halo nucleus 15 C

The structure of (15)C, with an s(1/2) neutron weakly bound to a closed-neutron shell nucleus (14)C, makes it a prime candidate for a one-neutron halo nucleus. We have for the first time studied the cross section for the fusion-fission reaction (15)C+(232)Th at energies in the vicinity of the Coulomb barrier and compared it to the yield of the neighboring (14)C+(232)Th system measured in the same experiment. At sub-barrier energies, an enhancement of the fusion yield by factors of 2-5 was observed for (15)C, while the cross sections for (14)C match the trends measured for (12,13)C.

Direct Measurement of the

In our Letter [Phys. Rev. Lett. 112, 152701 (2014)] we reported the direct measurement of the 23Naðα; pÞ26Mg reaction cross section at energies relevant for the production of Galactic Al. Our results, which relied on the extracted absolute cross sections given in Table I, have been found to be in error, overestimating the reported cross sections by a factor of 100. In the experiment, protons from the reaction were measured in an annular silicon strip detector placed downstream from a cryogenic He gas target. The cross sections were normalized to the yield of scattered Na ions from a separate Au foil in an upstream monitor detector. The data acquisition system was triggered by a logic “OR” of the proton detector and the “downscaled” monitor detector. The monitor detector rate was downscaled in order to reduce dead time in the data acquisition system. The down-scale factor was n 1⁄4 100, while in the analysis, the factor was mistakenly taken as n 1⁄4 1. Therefore, the cross section numbers given in Table I should be divided by a factor of 100. The stellar rate reported in our Letter should also be down scaled by the same factor of 100, which makes it in agreement, within the experimental uncertainties, with the recommended rate. This problem came to light due to results from recent experiments where the same reaction was studied in regular and inverse kinematics [1,2]. Those studies obtained similar results and were in disagreement with our measurement. A subsequent experiment by our group was carried out with a different technique to verify the results. In this experiment, an active target and detector system measures both the heavy Mg recoils as well as the incoming Na beam, thus avoiding normalization errors [3]. The new results [3] are in agreement with the reported results [1,2] and also with the values in our Letter, within their experimental uncertainties, if the down-scale factor is correctly included.

^{23}

In our Letter [Phys. Rev. Lett. 112, 152701 (2014)] we reported the direct measurement of the 23Naðα; pÞ26Mg reaction cross section at energies relevant for the production of Galactic Al. Our results, which relied on the extracted absolute cross sections given in Table I, have been found to be in error, overestimating the reported cross sections by a factor of 100. In the experiment, protons from the reaction were measured in an annular silicon strip detector placed downstream from a cryogenic He gas target. The cross sections were normalized to the yield of scattered Na ions from a separate Au foil in an upstream monitor detector. The data acquisition system was triggered by a logic “OR” of the proton detector and the “downscaled” monitor detector. The monitor detector rate was downscaled in order to reduce dead time in the data acquisition system. The down-scale factor was n 1⁄4 100, while in the analysis, the factor was mistakenly taken as n 1⁄4 1. Therefore, the cross section numbers given in Table I should be divided by a factor of 100. The stellar rate reported in our Letter should also be down scaled by the same factor of 100, which makes it in agreement, within the experimental uncertainties, with the recommended rate. This problem came to light due to results from recent experiments where the same reaction was studied in regular and inverse kinematics [1,2]. Those studies obtained similar results and were in disagreement with our measurement. A subsequent experiment by our group was carried out with a different technique to verify the results. In this experiment, an active target and detector system measures both the heavy Mg recoils as well as the incoming Na beam, thus avoiding normalization errors [3]. The new results [3] are in agreement with the reported results [1,2] and also with the values in our Letter, within their experimental uncertainties, if the down-scale factor is correctly included.

Na(

Using an array of high-purity Compton-suppressed germanium detectors, we performed an independent measurement of the

\alpha

\beta

,p)

-decay branching ratio from

^{26}

^{12}\mathrm{B}

Mg Reaction Cross Section at Energies Relevant for the Production of Galactic

to the second-excited (Hoyle) state in