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The astrophysical $S$-factor for the radiative proton capture reaction on $^7$Be ($S_{17}$) at low energies is affected by the $s$-wave scattering lengths. We report the measurement of elastic and inelastic scattering cross sections for the $^7$Be+p system in the center-of-mass energy range 0.474 - 2.740 MeV and center-of-mass angular range of 70$^\circ$- 150$^\circ$. A radioactive $^7$Be beam produced at Oak Ridge National Laboratory's (ORNL) Holifield Radioactive Ion Beam Facility was accelerated and bombarded a thin polypropylene (CH$_{2}$)$_\text n$ target. Scattered ions were detected in the segmented Silicon Detector Array. Using an $\textit{R}$-matrix analysis of ORNL and Louvain-la-Neuve cross section data, the $s$-wave scattering lengths for channel spins 1 and 2 were determined to be 17.34$^{+1.11}_{-1.33}$ and -3.18$^{+0.55}_{-0.50}$ fm, respectively. The uncertainty in the $s$-wave scattering lengths reported in this work is smaller by a factor of 5-8 compared to the previous measurement, which may reduce the overall uncertainty in $S_{17}$ at zero energy. The level structure of $^8$B is discussed based upon the results from this work. Evidence for the existence of 0$^+$ and 2$^+$ levels in $^8$B at 1.9 and 2.21 MeV, respectively, is observed.

The $^{15}$O($\alpha$,$\gamma$)$^{19}$Ne reaction is responsible for breakout from the hot CNO cycle in Type I x-ray bursts. Understanding the properties of resonances between $E_x = 4$ and 5 MeV in $^{19}$Ne is crucial in the calculation of this reaction rate. The spins and parities of these states are well known, with the exception of the 4.14- and 4.20-MeV states, which have adopted spin-parities of 9/2$^-$ and 7/2$^-$, respectively. Gamma-ray transitions from these states were studied using triton-$\gamma$-$\gamma$ coincidences from the $^{19}$F($^{3}$He,$t\gamma$)$^{19}$Ne reaction measured with GODDESS (Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies) at Argonne National Laboratory. The observed transitions from the 4.14- and 4.20-MeV states provide strong evidence that the $J^\pi$ values are actually 7/2$^-$ and 9/2$^-$, respectively. These assignments are consistent with the values in the $^{19}$F mirror nucleus and in contrast to previously accepted assignments.

Recent calculations suggest that the rate of neutron capture by 130Sn has a significant impact on late-time nucleosynthesis in the r-process. Direct capture into low-lying bound states is expected to be significant in neutron capture near the N=82 closed shell, so r- process reaction rates may be strongly impacted by the properties of neutron single particle states in this region. In order to investigate these properties, the (d, p) reaction has been studied in inverse kinematics using a 630 MeV beam of 130Sn (4.8 MeV/u) and a (CD2)n target. An array of Si strip detectors, including SIDAR and an early implementation of the ORRUBA, was used to detect reaction products. Results for the 130Sn(d, p)131Sn reaction are found to be very similar to those from the previously reported 132Sn(d, p)133Sn reaction. Direct-semidirect (n, ) cross section calculations, based for the first time on experimental data, are presented. The uncertainties in these cross sections are thus reduced by orders of magnitude from previous estimates.

The 28Si(p,3 He)26Al reaction was utilized for the first time to study the levels in 26Al, using a proton beam from the Holifield Radioactive Ion Beam Facility. Five previously unreported states in 26Al are observed and discussed, including Distorted Wave Born Approximation analysis. Proton-decay branching ratios consistent with previous studies and theoretical expectations were found by detecting decay protons from highly excited 26Al states in coincidence with the 3He particles.

Galactic 26Al is the first radioactive nucleus to be positively identified by -ray astronomy with detection of the 1.809 MeV ray associated with its decay. This nucleus is destroyed in astrophysical environments in the 26Al(p, )27Si and inelastic 26Al+p scattering reactions where properties of 27Si levels determine reaction rates. To investigate these properties, elastic and inelastic 26Al+p scattering reactions were measured between Ec.m. = 0.5 1.5 MeV at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). A candidate for a new resonance in the 26Al(p, )27Si reaction was identified. Upper limits were also set on the strengths of postulated resonances and on the cross section of the inelastic reaction, but there is little effect on current reaction rate calculations.

A good understanding of the level structure of ${}^{19}\mathrm{Ne}$ around the proton threshold is critical to estimating the destruction of long-lived ${}^{18}\mathrm{F}$ in novae. Here we report the properties of levels in ${}^{19}\mathrm{Ne}$ in the excitation energy range of 6.9 $\ensuremath{\leqslant}$ ${E}_{x}$ $\ensuremath{\leqslant}$ 8.4 MeV studied via the proton-transfer ${}^{18}\mathrm{F}(d,n){\mathrm{Ne}}^{*}$ reaction at the Holifield Radioactive Ion Beam Facility. The populated ${}^{19}\mathrm{Ne}$ levels decay by breakup into $p+{}^{18}\mathrm{F}$ and $\ensuremath{\alpha}+{}^{15}\mathrm{O}$ particles. The results presented in this manuscript are those of levels that are simultaneously observed from the breakup into both channels. An $s$-wave state is observed at 1468 keV above the proton threshold, which is a potential candidate for a predicted broad ${J}^{\ensuremath{\pi}}$ $=$ 1/2${}^{+}$ state. The proton and $\ensuremath{\alpha}$ partial widths are deduced to be ${\ensuremath{\Gamma}}_{p}$ $=$ 228 $\ifmmode\pm\else\textpm\fi{}$ 50 keV and ${\ensuremath{\Gamma}}_{\ensuremath{\alpha}}$ $=$ 130 $\ifmmode\pm\else\textpm\fi{}$ 30 keV for this state.

Simultaneous measurement of the proton-transfer {sup 18}F(d, n){sup 19}Ne and neutron-transfer {sup 18}F(d, p){sup 19}F reactions were performed with a {sup 18}F radioactive beam at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The experiments clarify the nuclear structure of {sup 19}Ne near the proton threshold, which is relevant for understanding the rates of proton-induced reactions on {sup 18}F in novae. Analogs for several states in the mirror nucleus {sup 19}F have not yet been identified in {sup 19}Ne, indicating that the level structure of {sup 19}Ne in this region is incomplete. We observed 15 levels in {sup 19}Ne from the {sup 18}F(d, n){sup 19}Ne measurement and 18 levels in {sup 19}F from the {sup 18}F(d, p){sup 19}F measurement. Angular distributions were extracted for all strongly populated states and compared to distorted-wave Born approximation calculations. The angular distributions for all the known states in the two nuclei determined in this work are consistent with their previously assigned spins and parities. The spectroscopic factors determined for these levels in the two nuclei are reported.

Big Bang nucleosynthesis calculations, constrained by the Wilkinson Microwave Anisotropy Probe results, produce {sup 7}Li abundances almost a factor of four larger than those extrapolated from observations. Since primordial {sup 7}Li is believed to be mostly produced by the beta decay of {sup 7}Be, one proposed solution to this discrepancy is a resonant enhancement of the {sup 7}Be(d,p)2{alpha} reaction rate through the 5/2{sup +} 16.7-MeV state in {sup 9}B. The {sup 2}H({sup 7}Be,d){sup 7}Be reaction was used to search for such a resonance; none was observed. An upper limit on the width of the proposed resonance was deduced.

The ${}^{18}\mathrm{F}(p,\ensuremath{\alpha}){}^{15}\mathrm{O}$ reaction is the predominant destruction mechanism in novae of the radionuclide $^{18}\mathrm{F}$, a target of $\ensuremath{\gamma}$-ray observatories. Thus, its rate is important for understanding $^{18}\mathrm{F}$ production in novae. We have studied resonances in the ${}^{18}\mathrm{F}+p$ system by making a measurement of a proton-transfer reaction ${}^{18}\mathrm{F}(d,n)$. We have observed 15 $^{19}\mathrm{Ne}$ levels, 5 of which are below the proton threshold, including a subthreshold state, which has significant ${l}_{p}=0$ strength. Our data provide a direct determination of the spectroscopic strength of these states and new constraints on their spins and parities, thereby resolving a controversy, which involves the 8- and 38-keV resonances. The ${}^{18}\mathrm{F}(p,\ensuremath{\alpha}){}^{15}\mathrm{O}$ reaction rate is reevaluated, which takes the subthreshold resonance and other new information determined in this experiment into account.

Several resonances in $^{25}\mathrm{Al}$($p,\ensuremath{\gamma}$)$^{26}\mathrm{Si}$ have been studied via the $^{28}\mathrm{Si}$($p,t$)$^{26}\mathrm{Si}$ 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 $^{26}\mathrm{Si}$ above the proton threshold in order to determine branching ratios. A resonance at $5927\ifmmode\pm\else\textpm\fi{}4$ keV has been experimentally confirmed as the first $\ensuremath{\ell}=0$ state above the proton threshold, with a proton branching ratio consistent with one.

The level structure of 22Na has been studied at the Holifield Radioactive Ion Beam Facility in Oak Ridge National Laboratory using the 24Mg(p,3He)22Na reaction. 41 and 41.5 MeV proton beams were generated by 25 MV tandem accelerator and bombarded isotopically enriched 24Mg targets. Angular distributions of recoiling 3He particles were extracted by using a segmented annular silicon strip detector array. Spins and parities for ten levels were constrained through a distorted wave Born approximation analysis of angular distributions including three above the proton threshold at 6.739 MeV.

We directly measure the {sup 17}F(p,{gamma}){sup 18}Ne resonant reaction using a mixed beam of {sup 17}F and {sup 17}O at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory (ORNL). The astrophysically important 3{sup +} resonance at {approx}600 keV above the proton threshold in {sup 18}Ne is found to have a partial width {Gamma}{sub {gamma}} = 56 {+-} 24(stat) {+-} 30(sys) meV, in reasonable agreement with the theoretically predicted width. A 2{sigma} upper limit on the direct capture of S(E) = 65 keV b is determined at an energy of 800 keV. Experimental techniques and astrophysical implications are discussed.

The {sup 18}Ne({alpha},p){sup 21}Na reaction plays a crucial role in the ({alpha},p) process, which leads to the rapid proton capture process in x-ray bursts. The reaction rate depends upon properties of {sup 22}Mg levels above the {alpha} threshold at 8.14 MeV. Despite recent studies of these levels, only the excitation energies are known for most with no constraints on the spins. We have studied the {sup 24}Mg(p,t){sup 22}Mg reaction at the Oak Ridge National Laboratory (ORNL) Holifield Radioactive Ion Beam Facility (HRIBF), and by measuring the angular distributions of outgoing tritons, we provide some of the first experimental constraints on the spins of astrophysically important {sup 18}Ne({alpha},p){sup 21}Na resonances.

The rate of the (17)F(p,gamma)(18)Ne reaction is important in various astrophysical events. A previous (17)F(p,p)(17)F measurement identified a 3;{+} state providing the strongest resonance contribution, but the resonance strength was unknown. We have directly measured the (17)F(p,gamma)(18)Ne reaction using a mixed beam of (17)F and (17)O at ORNL. The resonance strength for the 3;{+} resonance in (18)Ne was found to be omegagamma = 33 +/- 14(stat) +/-1 7(syst) meV, corresponding to a gamma width of Gamma_{gamma} = 56 +/- 24(stat) +/- 30(syst) meV. An upper limit on the direct capture of S(E)

We have developed a novel technique for measurements of low-energy $(p,\ensuremath{\alpha})$ reactions using heavy-ion beams and a differentially pumped windowless gas target. We applied this new approach to study the 183 keV resonance in the $^{17}\mathrm{O}$($p,\ensuremath{\alpha}$)$^{14}\mathrm{N}$ reaction. We report a (center-of-mass) resonance energy of ${E}_{r}=183.5\genfrac{}{}{0}{}{+0.1}{\ensuremath{-}0.4}$ keV and a resonance strength of $\ensuremath{\omega}{\ensuremath{\gamma}}_{p\ensuremath{\alpha}}=(1.70\ifmmode\pm\else\textpm\fi{}0.15)$ meV, and we set an upper limit (95% confidence) on the total width of the state of $\ensuremath{\Gamma}l0.1$ keV. This resonance is important for the $^{17}\mathrm{O}$($p,\ensuremath{\alpha}$)$^{14}\mathrm{N}$ reaction rate, and we find that $^{18}\mathrm{F}$ production is significantly decreased in low-mass ONeMg novae but less affected in more energetic novae. We also report the first determination of the stopping power for oxygen ions in hydrogen gas near the peak of the Bragg curve ($E=193$ keV/u) to be $(63\ifmmode\pm\else\textpm\fi{}1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ eV cm${}^{2}$.

The $^{28}\mathrm{Si}$($p,t$)$^{26}\mathrm{Si}$ reaction has been studied to resolve a controversy surrounding the properties of the $^{26}\mathrm{Si}$ level at 5.914 MeV and its contribution to the $^{25}\mathrm{Al}$($p,\ensuremath{\gamma}$)$^{26}\mathrm{Si}$ reaction rate in novae, which affects interpretations of galactic $^{26}\mathrm{Al}$ observations. Recent studies have come to contradictory conclusions regarding the spin of this level (${0}^{+}$ or ${3}^{+}$), with a ${3}^{+}$ assignment implying a large contribution by this level to the $^{25}\mathrm{Al}$($p,\ensuremath{\gamma}$)$^{26}\mathrm{Si}$ reaction rate. We have extended our previous study [Bardayan et al., Phys. Rev. C 65, 032801(R) (2002)] to smaller angles and find the angular distribution of tritons populating the 5.914-MeV level in the $^{28}\mathrm{Si}$($p,t$)$^{26}\mathrm{Si}$ reaction to be consistent with either a ${2}^{+}$ or ${3}^{+}$ assignment. We have calculated reaction rates under these assumptions and used them in a nova nucleosynthesis model to examine the effects of the remaining uncertainties in the $^{25}\mathrm{Al}$($p,\ensuremath{\gamma}$)$^{26}\mathrm{Si}$ rate on $^{26}\mathrm{Al}$ production in novae.

The interference effects among ${J}^{\ensuremath{\pi}}=3/{2}^{+}$ resonances in the $^{18}\mathrm{F}+p$ system have not been previously measured. $R$-matrix calculations show that the cross sections above the ${E}_{c.m.}=665$ keV resonance are sensitive to the interference between the ${E}_{c.m.}=8$, 38, and 665 keV resonances. An excitation function for the $^{1}\mathrm{H}$($^{18}\mathrm{F}$,\ensuremath{\alpha})$^{15}\mathrm{O}$ reaction has been measured in the energy range of ${E}_{c.m.}=663\text{\ensuremath{-}}877$ keV using radioactive $^{18}\mathrm{F}$ beams at the Holifield Radioactive Ion Beam Facility (HRIBF). By comparing the observed cross sections with the $R$-matrix calculations, we provide the first experimental constraints on the interference. Upper limits on proton widths (${\ensuremath{\Gamma}}_{p}$) of the ${E}_{c.m.}=827$ and 842 keV resonances have been set as well.