[en] Knowledge of the astrophysical ¹⁸F(p,α)¹⁵O rate is important for understanding gamma-ray emission from novae and heavy-element production in x-ray bursts. A state with E_x≅7.08 MeV in ¹⁹Ne provides an s-wave resonance and, depending on its properties, could dominate the ¹⁸F(p,α)¹⁵O rate. By measuring a kinematically complete ¹H(¹⁸F,p)¹⁸F excitation function with a radioactive ¹⁸F beam at the ORNL Holifield Radioactive Ion Beam Facility, we find that the ¹⁹Ne state lies at a center-of-mass energy of 665.3±1.7 keV (E_x=7077±2 keV), has a total width of 38.5±3.4 keV, and a proton partial-width of 15.8±1.6 keV

No abstract available

[en] Neutron transfer (d,p) reactions have been measured with rare isotope beams of ¹³²Sn, ¹³⁰Sn and ¹³⁴Te accelerated to ∼4.5 MeV/u interacting with CD₂ targets. Reaction protons were detected in an early implementation of the ORRUBA array of position-sensitive silicon strip detectors. Neutron excitations in the 2f_7/2, 3p_3/2, 3p_1/2 and 2f_5/2 orbitals were populated.

[en] The 19F nucleus has been studied extensively. However, there have been no comprehensive experimental studies of 18F+n single-particle components in 19F, and no measure of neutron vacancies in the 18F ground state, as such experiments require a (radioactive) 18F target or beam. We have used the 2H(18F,p)19F reaction to selectively populate states in 19F that are of 18F+n character. The 108.5-MeV radioactive 18F+9 beam was provided by the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. Proton-recoil coincidence data were taken for both -decaying and particle-stable final states. Angular distributions and spectroscopic factors were measured for nine proton groups, corresponding to 13 states in 19F. The results are compared to shell model calculations

[en] The level structure of ²⁵Al has been studied at the ORNL Holifield Radioactive Ion Beam Facility by measuring the angular and energy distributions of α particles from the ²⁸Si(p,α)²⁵Al reaction. Proton beams (∼10 nA) at laboratory energies of 40 and 42 MeV were generated by the 25 MV tandem accelerator and bombarded a natural silicon target (50 μg/cm²). Seventeen levels were observed and spins for several were constrained through a distorted-wave Born approximation analysis of the angular distributions.

[en] A new program to measure (d,p) reactions on rare isotopes of fission fragments has been established at Oak Ridge National Laboratory. Initial measurements on N=50 isotones and prospects for Z=50 experiments are reported

[en] Half of the elements heavier than iron are believed to be produced through the rapid neutron-capture process ($r$-process). The astrophysical environment(s) where the $r$-process occurs remains an open question, even after recent observations of neutron-star mergers and the associated kilonova. Features in the abundance pattern of $r$-process ashes may provide critical insight for distinguishing contributions from different possible sites, including neutron-star mergers and core-collapse supernovae. In particular, the largely unknown neutron-capture reaction rates on neutron-rich unstable nuclei near ¹³²Sn could have a significant impact on the final $r$-process abundances. To better determine these neutron-capture rates, the ($d,p$) reaction has been measured in inverse kinematics using radioactive ion beams of ¹²⁶Sn and ¹²⁸Sn and a stable beam of ¹²⁴Sn interacting with a (CD₂)${}_n$ target. An array of position-sensitive silicon strip detectors, including the Super Oak Ridge Rutgers University Barrel Array, was used to detect light reaction products. In addition to the present measurements, previous measurements of ^130,132Sn($d,p$) were reanalyzed using state-of-the-art reaction theory to extract a consistent set of spectroscopic factors for ($d,p$) reactions on even tin nuclei between the heaviest stable isotope ¹²⁴Sn and doubly magic ¹³²Sn. The spectroscopic information was used to calculate direct-semidirect ($n,\text{γ<!-- ?? -->}$) cross sections, which will serve as important input for r-process abundance calculations.

[en] A recent discussion of the ¹⁸F(p,α) reaction [N. de Sereville et al., Phys. Rev. C 79, 015801 (2009)] questions our previous analysis of interference effects in this reaction. We address these questions and demonstrate that our previous analysis is indeed appropriate.

[en] Knowledge of the ¹⁸F(p,α)¹⁵O and ¹⁸F(p,γ)¹⁹Ne astrophysical reaction rates are important to understand γ-ray emission from nova explosions and heavy-element production in x-ray bursts. The rates for these reactions have been uncertain, in part due to a lack of a comprehensive examination of the available structure information in the compound nucleus ¹⁹Ne. We have examined the latest experimental measurements with radioactive and stable beams, collected all the structure information in the nucleus ¹⁹Ne and its mirror ¹⁹F, and made estimates of unmeasured ¹⁹Ne nuclear-level parameters. These parameters will be useful for future reaction rate calculations

[en] Several resonances in ²⁵Al(p,γ)²⁶Si have been studied via the ²⁸Si(p,t)²⁶Si reaction. Triton energies and angular distributions were measured using a segmented annular detector array. An additional silicon detector array was used to simultaneously detect the coincident protons emitted from the decay of states in ²⁶Si above the proton threshold in order to determine branching ratios. A resonance at 5927±4 keV has been experimentally confirmed as the first l=0 state above the proton threshold, with a proton branching ratio consistent with one.