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New measurements of photofission and photoneutron reactions on $^{238}$U and $^{232}$Th in the Giant Dipole Resonance (GDR) energy region have been performed at the laser Compton-scattering $\gamma$-ray source of the NewSUBARU synchrotron radiation facility using a high-and-flat efficiency moderated $^3$He detection array. The neutron-multiplicity sorting of high-multiplicity fission neutron coincidence events has been performed using a dedicated energy dependent, multiple firing statistical treatment. The photoneutron $(\gamma,\,in)$ with $i$~=~1~--~3 and photofission $(\gamma,\,F)$ reactions have been discriminated by considering a Gaussian distribution of prompt-fission-neutron (PFN) multiplicities predicted by the theory of evaporation in sequential neutron emission from excited fission fragments. We report experimental $(\gamma,\,n)$, $(\gamma,\,2n)$, $(\gamma,\,3n)$ and $(\gamma,\,F)$ cross sections, average energies of PFNs and of $(\gamma,\,in)$ photoneutrons, as well as the mean number of PFNs per fission act and the width of the PFNs multiplicity distribution. Based on these primary experimental results and combined with reasonable assumptions, we extract also the first- and second-chance fission contributions. The new experimental results are compared with statistical-model calculations performed with the EMPIRE-3.2 Malta and TALYS-1.964 codes on the present data and with prompt fission emission calculations obtained with the Los Alamos model in the frame of the most probable fragmentation approach with and without sequential emission.

We have studied the uncharacteristic behavior of the measured values of the isoscalar and isovector centroid energies, ECEN, of giant resonances with multipolarity L=0-3 in 44Ca, 54Fe, 64,68Zn and 56,58,60,68Ni. For this purpose, we carried out calculations of ECEN within the spherical Hartree-Fock (HF)-based random phase approximation (RPA) theory with 33 different Skyrme-type effective nucleon-nucleon interactions. We have also determined the Pearson linear correlation coefficients between the calculated centroid energies and the various nuclear matter (NM) properties associated with each interaction and determined the sensitivity of ECEN to NM properties. We compared the calculated centroid energies of the giant resonances with experimental data and discuss the results. We note in particular, that we obtain good agreement between the calculated ECEN of isovector giant dipole resonance and the available experimental data.

Photoneutron cross sections were measured for $^{137}$Ba and $^{138}$Ba at energies below two-neutron threshold using quasi-monochromatic $\gamma$-ray beams produced in laser Compton-scattering at the NewSUBARU synchrotron radiation facility. The photoneutron data are used to constrain the $\gamma$-ray strength function on the basis of the Hartree-Fock-Bogolyubov plus quasi-particle random phase approximation using the Gogny D1M interaction. Supplementing the experimentally constrained $\gamma$-ray strength function with the zero-limit E1 and M1 contributions which are unique to the deexcitation mode, we discuss radiative neutron capture cross sections relevant to the s-process nucleosynthesis of barium isotopes in the vicinity of the neutron magic number 82., Comment: arXiv admin note: substantial text overlap with arXiv:1811.00291, arXiv:1804.07654

Photoneutron cross sections were measured for $^{203}$Tl and $^{205}$Tl at energies between the one- and two-neutron thresholds using quasi-monochromatic $\gamma$-ray beams produced in laser Compton-scattering at the NewSUBARU synchrotron radiation facility. Our new measurement results in cross sections significantly different from the previously reported bremsstrahlung experiment, leading to rather different GDR parameters, in particular to lower GDR peak energies and higher peak cross sections. The photoneutron data are used to constrain the $\gamma$-ray strength function on the basis of the Hartree-Fock-Bogolyubov plus quasi-particle random phase approximation using the Gogny D1M interaction. Supplementing the experimentally constrained $\gamma$-ray strength function with the zero-limit E1 and M1 contributions for the de-excitation mode, we estimate the Maxwellian-averaged cross section for the s-process branching-point nucleus $^{204}$Tl in the context of the $^{205}$Pb - $^{205}$Tl chronometry., Comment: 8 pages, 10 figures, to be submitted to PRC

Photoneutron cross sections were measured for $^{58}$Ni, $^{60}$Ni, $^{61}$Ni, and $^{64}$Ni at energies between the one-neutron and two-neutron thresholds using quasi-monochromatic $\gamma$-ray beams produced in laser Compton-scattering at the NewSUBARU synchrotron radiation facility. The new photoneutron data are used to extract the $\gamma$-ray strength function above the neutron threshold complementing the information obtained by the Oslo method below the threshold. We discuss radiative neutron capture cross sections and the Maxwellian-averaged cross sections for Ni isotopes including $^{63}$Ni, a branching point nucleus along the weak s-process path. The cross sections are calculated with the experimentally constrained $\gamma$-ray strength functions from the Hartree-Fock-Bogolyubov plus quasi-particle-random phase approximation based on the Gogny D1M interaction for both $E1$ and $M1$ components and supplemented with the $M1$ upbend., Comment: 9 pages, 7 figures, re-submitted to PRC

In this work, we present new data on the $^{89}$Y($\gamma$,n) cross section studied with a quasi-monochromatic photon beam produced at the NewSUBARU synchrotron radiation facility in Japan contributing torwards resolving a long standing discrepancy between existing measurements of this cross section. Results for $\gamma$-ray strength function below threshold obtained by applying the Oslo method to $^{89}$Y($p,p'\gamma$)$^{89}$Y coincidences combined with the $^{89}$Y($\gamma$,n) data this providing experimental data for the $\gamma$-ray strength function of $^{89}$Y for $\gamma$ energies in the range of $\approx 1.6$ Mev to $\approx$ 20 MeV. A low-energy enhancement is seen for $\gamma$-rays below $\approx 2.5$ MeV. Shell-model calculations indicate that this feature is caused by strong, low-energy $M1$ transitions at high excitation energies. The nuclear level density and $\gamma$-ray strength function have been extracted from $^{89}$Y($d,p \gamma$)$^{90}$Y coincidences using the Oslo method. Using the ($\gamma,n$) and ($d,p\gamma$) data as experimental constraints, we have calculated the $^{89}$Y($n,\gamma$)$^{90}$Y cross section with the TALYS reaction code. Our results have been compared with directly measured (n,$\gamma$) cross sections and evaluations. The $N=50$ isotope $^{89}$Y is an important bottleneck in the s-process and the magnitude of the $^{89}$Y(n,$\gamma)$ cross section is key to understanding how s-process stars produce heavy isotopes., Comment: 18 pages (including references) and 16 figures, to be submitted to PRC

Nuclear level densities and $\gamma$-ray strength functions have been extracted for $^{59, 60}\rm{Ni}$, using the Oslo method on data sets from the $^{60}$Ni($^{3}$He,$^{3}$He$^{\prime}\gamma$)$^{60}$Ni and $^{60}$Ni($^{3}$He,$\alpha\gamma$)$^{59}$Ni reactions. Above the neutron separation energy, S$_n$, we have measured the $\gamma$-ray strength functions for $^{61}$Ni and $^{60}$Ni in photoneutron experiments. The low-energy part of the $^{59,60}$Ni $\gamma$-ray strength functions show an increase for decreasing $\gamma$ energies. The experimental $\gamma$-ray strength functions are compared with $M1$ $\gamma$-ray strength functions calculated within the shell model. The $E1$ $\gamma$-ray strength function of $^{60}$Ni has been calculated using the QTBA framework. The QTBA calculations describe the data above $E_{\gamma}\approx$ 7 MeV, while the shell-model calculations agree qualitatively with the low energy part of the $\gamma$-ray strength function. Hence, we give a plausible explanation of the observed shape of the $\gamma$-decay strength.

The photo-neutron cross sections of $^{162,163}\rm{Dy}$ have been measured for the first time in an energy region from the neutron threshold ($S_n$) up to $\approx$ $13$~MeV. The ($\gamma$,n) reaction was induced with quasi-monochromatic laser Compton-scattered $\gamma$ rays, produced at the NewSUBARU laboratory. The corresponding $\gamma$-ray strength functions ($\gamma$SF) have been calculated from the photo-neutron cross sections. The data are compared to reanalyzed $\gamma$SFs of $^{160-164}\rm{Dy}$, which are measured below $S_n$. The excellent agreement with the photo-neutron data at $S_n$ confirms the principle of detailed balance. Thus, a complete $\gamma$SF is established covering in total the energy region of 1 MeV $\leq$ E$_{\gamma}$ $\leq$ 13 MeV. These mid-shell well-deformed dysprosium isotopes all show scissors resonances with very similar structures. We find that our data predict the same integrated scissors strength as ($\gamma,\gamma^\prime$) data when integrated over the same energy range, which shows that the scissors mode very likely is consistent with the generalized Brink hypothesis. Finally, using the $\gamma$SFs as input in the reaction code TALYS, we have deduced radiative neutron-capture cross sections and compared them to direct measurements. We find a very good agreement within the uncertainties, which gives further support to the experimentally determined $\gamma$SFs.

The $\gamma$-ray strength functions and level densities of $^{73,74}$Ge have been extracted up to the neutron separation energy S$_n$ from particle-$\gamma$ coincidence data using the Oslo method. Moreover, the $\gamma$-ray strength function of $^{74}$Ge above S$_n$ has been determined from photo-neutron measurements, hence these two experiments cover the range of E$_\gamma \approx$ 1-13 MeV for $^{74}$Ge. The obtained data show that both $^{73,74}$Ge display an increase in strength at low $\gamma$ energies. The experimental $\gamma$-ray strength functions are compared with $M1$ strength functions deduced from average $B(M1)$ values calculated within the shell model for a large number of transitions. The observed low-energy enhancements in $^{73,74}$Ge are adopted in the calculations of the $^{72,73}$Ge(n,$\gamma$) cross sections, where there are no direct experimental data. Calculated reaction rates for more neutron-rich germanium isotopes are shown to be strongly dependent on the presence of the low-energy enhancement.

The Helioseismic and Magnetic Imager (HMI), on board the Solar Dynamics Observatory (SDO), will begin data acquisition in 2008. It will provide the first full disk, high temporal cadence observations of the full Stokes vector with a 0.5 arc sec pixel size. This will allow for a continuous monitoring of the Solar magnetic field vector. HMI data will advance our understanding of the small and large-scale magnetic field evolution, its relation to the solar and global dynamic processes, coronal field extrapolations, flux emergence, magnetic helicity and the nature of the polar magnetic fields. We summarize HMI's expected operation modes, focusing on the polarization cross-talk induced by the solar oscillations and how this affects the magnetic field vector determinations., Comment: 4 pages, 2 figures. to appear in the proceedings of the Solar Polarizaton Workshop IV

Cross sections of the $^{186}$W, $^{187}$Re, $^{188}$Os($\gamma,n$) reactions were measured using quasi-monochromatic photon beams from laser Compton scattering (LCS) with average energies from 7.3 to 10.9 MeV. The results are compared with the predictions of Hauser-Feshbach statistical calculations using four different sets of input parameters. In addition, the inverse neutron capture cross sections were evaluated by constraining the model parameters, especially the $E1$ strength function, on the basis of the experimental data. The present experiment helps to further constrain the correction factor $F_{\sigma}$ for the neutron capture on the 9.75 keV state in $^{187}$Os. Implications of $F_{\sigma}$ to the Re-Os cosmochronology are discussed with a focus on the uncertainty in the estimate of the age of the Galaxy., Comment: 11 pages

The neutron capture cross section of the unstable s-process branching nucleus 185W has been derived from experimental data of the inverse 186W(g,n)185W photodisintegration taken with monochromatic photon beams from laser Compton scattering. The result of sigma = 553 +- 60 mb at kT = 30 keV leads to a relatively high effective neutron density in the classical s-process of N_n = 4.7 \times 10^8 cm^-3. A realistic model for the s-process in thermally pulsing AGB stars overestimates the abundance of 186Os significantly because of the relatively small neutron capture cross section of 185W., Comment: 10 pages, 3 figures

Asymptotic normalization coefficients (ANCs) for 8Li->7Li+n have been extracted from the neutron transfer reaction 13C(7Li,8Li)12C at 63 MeV. These are related to the ANCs in 8B->7Be+p using charge symmetry. We extract ANCs for 8B that are in very good agreement with those inferred from proton transfer and breakup experiments. We have also separated the contributions from the p_1/2 and p_3/2 components in the transfer. We find the astrophysical factor for the 7Be(p,gamma)8B reaction to be S_17(0)=17.6+/-1.7 eVb. This is the first time that the rate of a direct capture reaction of astrophysical interest has been determined through a measurement of the ANCs in the mirror system., Comment: 5 pages, 3 figures, 2 tables

We present the results of a search for optical model potentials for use in the description of elastic scattering and transfer reactions involving stable and radioactive p-shell nuclei. This was done in connection with our program to use transfer reactions to obtain data for nuclear astrophysics, in particular for the determination of the astrophysical S_17 factor for 7Be(p,\gamma)8B using two (7Be,8B) proton transfer reactions. Elastic scattering was measured using 7Li, 10B, 13C and 14N projectiles on 9Be and 13C targets at or about E/A=10 MeV/nucleon. Woods-Saxon type optical model potentials were extracted and are compared with potentials obtained from a microscopic double folding model. We use these results to find optical model potentials for unstable nuclei with emphasis on the reliability of the description they provide for peripheral proton transfer reactions. We discuss the uncertainty introduced by the procedure in the prediction of the DWBA cross sections for the (7Be,8B) reactions used in extracting the astrophysical factor S_17(0)., Comment: 16 pages, LaTEX file, 9 figures (PostScript files)

The ${}^{16}O ({}^{3}He,d) {}^{17}F$ reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of ${}^{17}F$. The coefficients provide the normalization for the tails of the overlap functions for ${}^{17}F \to{}^{16}O + p$ and allow us to calculate the S-factors for ${}^{16}O (p,\gamma){}^{17}F$ at astrophysical energies. The calculated S-factors are compared to measurements and found to be in very good agreement. This provides the first test of this indirect method to determine astrophysical direct capture rates using transfer reactions. In addition, our results yield S(0) for capture to the ground and first excited states in $^{17}F$, without the uncertainty associated with extrapolation from higher energies., Comment: 6 pages, 2 figures

The $^{13}C(^{14}N,^{13}C)^{14}N$ proton exchange reaction has been measured at an incident energy of 162 MeV. Angular distributions were obtained for proton transfer to the ground and low lying excited states in $^{14}N$. Elastic scattering of $^{14}N$ on $^{13}C$ also was measured out to the rainbow angle region in order to find reliable optical model potentials. Asymptotic normalization coefficients for the system $^{13}C+p\to {}^{14}N$ have been found for the ground state and the excited states at 2.313, 3.948, 5.106 and 5.834 MeV in $^{14}N$. These asymptotic normalization coefficients will be used in a determination of the S-factor for $^{7}Be(p,\gamma)^{8}B$ at solar energies from a measurement of the proton transfer reaction $^{14}N(^{7}Be,^{8}B)^{13}C$., Comment: 5 pages, 6 figures