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The 18F(p,$\alpha$) reaction determines the rate of destruction of 18F in novae. It represents the key nuclear physics uncertainty in modelling the calculated flux of annihilation radiation emitted following the radioactive decay of 18F. The major uncertainties relate to states representing s-wave resonances in the compound system, 19Ne. We report a first study of the 19F(3He, t)19Ne reaction at intermediate energies and forward angles. This reaction has a simple, model-independent, mechanism that we use here to identify states near the proton threshold energy in 19Ne corresponding to $\Delta L=0$ transitions. In particular, we observe a $\Delta L=0$ state at 6.13 MeV which could significantly affect the 18F(p,$\alpha$) astrophysical S-factor at nova burning temperatures.

Background: The $^{22}\mathrm{Ne}(\ensuremath{\alpha},n)^{25}\mathrm{Mg}$ reaction is the dominant neutron source for the slow neutron capture process ($s$ process) in massive stars, and contributes, together with $^{13}\mathrm{C}(\ensuremath{\alpha},n)^{16}\mathrm{O}$, to the production of neutrons for the $s$ process in asymptotic giant branch (AGB) stars. However, the reaction is endothermic and competes directly with $^{22}\mathrm{Ne}(\ensuremath{\alpha},\ensuremath{\gamma})^{26}\mathrm{Mg}$ radiative capture. The uncertainties for both reactions are large owing to the uncertainty in the level structure of $^{26}\mathrm{Mg}$ near the $\ensuremath{\alpha}$ and neutron separation energies. These uncertainties affect the $s$-process nucleosynthesis calculations in theoretical stellar models.Purpose: Indirect studies in the past have been successful in determining the energies and the $\ensuremath{\gamma}$-ray and neutron widths of the $^{26}\mathrm{Mg}$ states in the energy region of interest. But, the high Coulomb barrier hinders a direct measurement of the resonance strengths, which are determined by the $\ensuremath{\alpha}$ widths for these states. The goal of the present experiments is to identify the critical resonance states and to precisely measure the $\ensuremath{\alpha}$ widths by $\ensuremath{\alpha}$-transfer techniques.Methods: The $\ensuremath{\alpha}$-inelastic scattering and $\ensuremath{\alpha}$-transfer measurements were performed on a solid $^{26}\mathrm{Mg}$ target and a $^{22}\mathrm{Ne}$ gas target, respectively, using the Grand Raiden Spectrometer at the Research Center for Nuclear Physics in Osaka, Japan. The $(\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}})$ measurements were performed at $0.{45}^{\ensuremath{\circ}}, 4.{1}^{\ensuremath{\circ}}, 8.{6}^{\ensuremath{\circ}}$, and $11.{1}^{\ensuremath{\circ}}$ and the $(^{6}\mathrm{Li},d)$ measurements at ${0}^{\ensuremath{\circ}}$ and ${10}^{\ensuremath{\circ}}$. The scattered $\ensuremath{\alpha}$ particles and deuterons were detected by the focal plane detection system consisting of multiwire drift chambers and plastic scintillators. The focal plane energy calibration allowed the study of $^{26}\mathrm{Mg}$ levels from ${E}_{x}$ = 7.69--12.06 MeV in the $(\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}})$ measurement and ${E}_{x}$ = 7.36--11.32 MeV in the $(^{6}\mathrm{Li},d)$ measurement.Results: Six levels (${E}_{x}$ = 10717, 10822, 10951, 11085, 11167, and 11317 keV) were observed above the $\ensuremath{\alpha}$ threshold in the region of interest (10.61--11.32 MeV). The $\ensuremath{\alpha}$ widths were calculated for these states from the experimental data. The results were used to determine the $\ensuremath{\alpha}$-capture induced reaction rates.Conclusion: The energy range above the $\ensuremath{\alpha}$ threshold in $^{26}\mathrm{Mg}$ was investigated using a high resolution spectrometer. A number of states were observed for the first time in $\ensuremath{\alpha}$-scattering and $\ensuremath{\alpha}$-transfer reactions. The excitation energies and spin-parities were determined. Good agreement is observed for previously known levels in $^{26}\mathrm{Mg}$. From the observed resonance levels the ${E}_{x}$ = 10717 keV state has a negligible contribution to the $\ensuremath{\alpha}$-induced reaction rates. The rates are dominated in both reaction channels by the resonance contributions of the states at ${E}_{x}$ = 10951, 11167, and 11317 keV. The ${E}_{x}$ = 11167 keV state has the most appreciable impact on the $(\ensuremath{\alpha},\ensuremath{\gamma})$ rate and therefore plays an important role in the prediction of the neutron production in $s$-process environments.

Interaction cross sections (sigma(1)) for Me isotopes from the stability line to the vicinity of the neutron drip line have been measured at around 240 MeV/nucleon using BigRIPS at RIBF, RIKEN, The sigma(1) for Ne27-32 in every case exceed the systematic mass-number dependence of sigma(1) for stable nuclei, which can be explained by considering the nuclear deformation. In particular the sigma(1) for Ne-29 and Ne-31 are significantly greater than those of their neighboring nuclides. These enhancements of sigma(1) for Ne-29 and Ne-31 cannot be explained by a single-particle model calculation under the assumption that the valence neutron of Ne-29 (Ne-31) occupies the 0d(3/2) (0f(7/2)) orbital, as expected from the standard spherical shell ordering. The present data suggest an s dominant halo structure of Ne-29 and s- or p-orbital halo in Ne-31. (C) 2011 Elsevier B.V. All rights reserved.

Interaction cross sections (σI) for Ne isotopes from the stability line to the vicinity of neutron-drip line have been measured using the RIBF facility at RIKEN. Measurements have been performed for 20–32 Ne on C target at energies around 240 MeV/nucleon. A large enhancement of σI beyond the systematics of stable nuclei have been observed for neutron-rich Ne isotopes. The possible halo structures with lower orbital angular momentum for 29,31 Ne are discussed by the preliminary analysis.

The degrees of polarization of proton rich nucleus 28P produced in charge exchange reactions 28Si + 9Be → 28P + X, and 28Si + 1H → 28P + X have been observed at 100A MeV. Utilizing thus obtained polarized nuclei, the magnetic moment of 28P was remeasured, and |μ(28P)| = 0.3115 (34) μN was obtained. β-nuclear quadrupole resonance (β-NQR) of 28P implanted in α-Al2O3 have been observed for the first time, in order to measure the electric quadrupole moment of this nucleus.

Interaction cross sections ( σ I ) for neutron-rich Ne isotopes, 28–32Ne on C target have been measured at 240A MeV using the RIBF at RIKEN. A large enhancement of σ I beyond the systematics of stable nuclei have been observed for neutron-rich Ne isotopes, particularly for 31Ne. The possible halo structure for 29,31Ne which would be caused by the lowering of the pf-shell and nuclear deformation of Ne isotopes are discussed by the preliminary analysis.

Ratios of equilibrium charge-state yields for singly to doubly ionized He-3 ions at an energy of 420 MeV were measured using the Grand Raiden magnetic spectrometer at RCNP. Targets with atomic numbers of 6, 12, 28, 40, 50 and 82 were used. It is found that theoretical calculations for atomic electron-capture and stripping cross sections, which have been successful in describing the data up to beam energies of 200 MeV, are also applicable at this higher energy. However, where at the lower energies the stripping cross sections were calculated with a combination of models by Bohr and Gillespie, the best description of the data at E(He-3) = 420 MeV is obtained when using only the model by Gillespie. The experimental results are also compared with calculations using the code CHARGE, originally developed for fast, heavy (Z > 29) projectiles, to test the extrapolation to low-Z projectiles. It is found that the code underestimates the production of singly-charged He-3 ions, in particular for heavier target nuclei. (c) 2007 Elsevier B.V. All rights reserved.

The cluster structures of the excited states in 11B are studied by analyzing the isoscalar monopole and quadrupole strengths in the 11B(d,d′) reaction at E d = 200 MeV . The excitation strengths are compared with the predictions by the shell-model and antisymmetrized molecular-dynamics (AMD) calculations. It is found that the large monopole strength for the 3 / 2 3 − state at E x = 8.56 MeV is well described by the AMD calculation and is an evidence for a developed three-body 2 α + t cluster structure.

8 pages, 5 figures.-- PACS nrs.: 25.40.Ep, 25.70.De.-- ISI Article Identifier: 000247257800008., Published in the Proceedings of the 2nd International Conference on Collective Motion in Nuclei under Extreme Conditions (COMEX 2). Sankt Goar, Germany, June 20-23, 2006., Experimental technique for measuring proton inelastic scattering with high-resolution at 295 MeV and at forward angles including zero degrees have been successfully developed. An excitation energy resolution of less than 20 keV, good scattering angle resolution, low background condition, and reasonable background subtraction have been achieved. The experimental technique have been applied for several sd and pf shell nuclei for systematic study M1 and E1 excitations in nuclei. The experimental method and preliminary spectra are reported.

The cluster structures of the excited states in 11 B are studied by analyzing the isoscalar monopole and quadrupole strengths in the 11 B( d , d ′) reaction at E d = 200 MeV . The excitation strengths are compared with the predictions by the shell-model and antisymmetrized molecular-dynamics (AMD) calculations. It is found that the large monopole strength for the 3 / 2 3 − state at E x = 8.56 MeV is well described by the AMD calculation and is an evidence for a developed 2 α + t cluster structure.

The level structure of 30 S was studied at the NSCL by using neutron removal reactions with a radioactive 31 S beam. The γ -decay from excited states in 30 S was measured in a Ge-detector array. The results discussed for this work will reduce the uncertainties in the determination of the astrophysical 29 P(p, γ ) 30 S reaction rate under rp -process conditions.

The cluster structures of the excited states in 11B are studied by analyzing the isoscalar monopole and quadrupole strengths in the B 11 ( d , d ′ ) reaction at E d = 200 MeV . The excitation strengths are compared with the predictions by the shell-model and antisymmetrized molecular-dynamics (AMD) calculations. The large monopole strength for the 3 / 2 3 − state at E x = 8.56 MeV is well described by the AMD calculation and is suggested to be an evidence for a well developed 2 α + t cluster structure.

The electric dipole strength distribution in 120Sn between 5 and 22 MeV has been determined at RCNP Osaka from a polarization transfer analysis of proton inelastic scattering at E_0 = 295 MeV and forward angles including 0{\deg}. Combined with photoabsorption data an electric dipole polarizability \alpha_D(120Sn) = 8.93(36) fm^3 is extracted. The dipole polarizability as isovector observable par excellence carries direct information on the nuclear symmetry energy and its density dependence. The correlation of the new value with the well established \alpha_D(208Pb) serves as a test of its prediction by nuclear energy density functionals (EDFs). Models based on modern Skyrme interactions describe the data fairly well while most calculations based on relativistic Hamiltonians cannot., Comment: 6 pages, 4 figures

Differential cross sections of isoscalar and isovector spin-M1 (0(+)→1(+)) transitions are measured using high-energy-resolution proton inelastic scattering at E(p)=295 MeV on (24)Mg, (28)Si, (32)S, and (36)Ar at 0°-14°. The squared spin-M1 nuclear transition matrix elements are deduced from the measured differential cross sections by applying empirically determined unit cross sections based on the assumption of isospin symmetry. The ratios of the squared nuclear matrix elements accumulated up to E(x)=16 MeV compared to a shell-model prediction are 1.01(9) for isoscalar and 0.61(6) for isovector spin-M1 transitions, respectively. Thus, no quenching is observed for isoscalar spin-M1 transitions, while the matrix elements for isovector spin-M1 transitions are quenched by an amount comparable with the analogous Gamow-Teller transitions on those target nuclei.

Y. Fujita et al.; 15 pags.; 6 figs.; 7 tabs.; PACS number(s): 21.10.Hw, 25.55.Kr, 27.40.+z, 25.40.Ep

The electric dipole strength in 120Sn has been extracted from proton inelastic scattering experiments at E_p = 295 MeV and at forward angles including 0 degree. Below neutron threshoild it differs from the results of a 120Sn(gamma,gamma') experiment and peaks at an excitation energy of 8.3 MeV. The total strength corresponds to 2.3(2)% of the energy-weighted sum rule and is more than three times larger than what is observed with the (gamma,gamma') reaction. This implies a strong fragmentation of the E1 strength and/or small ground state branching ratios of the excited 1- states., 7 pages, 6 figures

Experimental method of measuring inelastic proton scattering with high-resolution at forward angles including zero degrees has been developed. An energy resolution of 20 keV and a scattering angle resolution of 0.5 degrees have been achieved as well as low background condition and a reliable background subtraction method. The experimental technique was applied to the 12 C (p,p′) reaction for studying the property of the second 0+ state at 7.7 MeV and a broad bump around Ex~10 MeV , where the presence of a 2+ state was reported from the 12 C (α,α′) measurement. Preliminary spectra and angular distributions are shown.

The cluster structures of the excited states in 11 B are studied by analyzing the isoscalar monopole and quadrupole strengths in the 11 B (d,d′) reaction at Ed = 200 MeV . The excitation strengths are compared with the predictions by the shell-model and antisymmetrized molecular-dynamics (AMD) calculations. It is found that the large monopole strength for the [Formula: see text] state at Ex = 8.56 MeV is well described by the AMD calculation and is an evidence for a developed 2α + t cluster structure.

The two charge exchange reactions 14N(d, 2He)14C and 14N(3He, t)14O were studied with high resolution in order to identify the Gamow–Teller (GT) strength distribution starting from the ground state (g.s.) of 14N in the β− and β+ directions. The isospin symmetry in the A = 14 mass system is investigated. An overview of the main features of the experimental investigation is summarized here.

In order to study the Gamow–Teller (GT) transitions in the fp-shell nucleus 64Cu, the 64Ni(3He, t)64Cu charge-exchange reaction was investigated at MeV/nucleon [1]. The outgoing tritons were momentum analysed by the Grand Raiden spectrometer at 0°. The very high energy resolution of 35 keV (FWHM) allowed the separation of individual levels in the excitation energy region from 0 to 3.5 MeV. An angular distribution analysis was performed for the observed transitions to these states. In addition to the ground state (g.s.), known to be a Jπ = 1+ GT state, several excited states showed L = 0 nature, making them candidates of GT states. At higher excitation energies, the level density becomes very high and a bump-like structure, the so-called GT Giant Resonance, dominates the spectrum.

Interactions of 150 MeV/amu 3 He ++ projectiles with solid gold targets have been studied at the isochronous cyclotron of the RCNP in Osaka. The 3 He + ions resulting from capture of the target electrons to the projectile were observed with the use of large magnetic spectrograph, Grand Raiden, set at θ = 0° with respect to the beam. The yield ratio of singly to doubly ionized helium ions emerging from thin gold foils, He + /He ++ , has been measured as a function of the foil thickness. Extrapolating the results to zero Au target thickness permits to determine the cross section values for electron stripping from 3 He + ions, σ STRIP = 1.05 × 10 −17 cm 2 , and for electron capture to 3 He ++ ions, σ CAP = 1.12 × 10 −25 cm 2 . The results obtained extend significantly the existing systematics for both processes to high (semi-relativistic) velocities. The collision strength deduced from the stripping cross sections deviates strongly from the theoretical predictions of Gillespie in absolute values as well as in the velocity dependence. It can, however, be well approximated by the simple Bohr formula for mid Z atoms. Also the capture data indicate the need to improve the theoretical approximations. A more detailed treatment of electrons captured from different shells in a high Z target is presumably needed. The astrophysical interest in the data of this kind for very light ions (hydrogen, helium) is indicated.

The analyzing power of the reaction p p→ppπ 0 has been measured at a beam energy of 390 MeV. The dependences of the analyzing power on the pion emission-angle and the relative momentum of two outgoing protons have been obtained. The angular dependence could be decomposed by Legendre polynomial and the relative contribution of the P 21 to the P 11 function is less than 4%. The momentum dependence of the analyzing power has been studied to obtain information about the pion-production mechanism. It has been deduced that pion production due to the long-range interaction plays an important role in the momentum dependence of the P -state amplitude.

Under the assumption that isospin is a good quantum number, symmetry is expected for the transitions from the ground states of T = 1, T z = ±1 nuclei to the common excited states of the T z = 0 nucleus situated between the two nuclei. The symmetry can be studied by comparing the strengths of Gamow-Teller (GT) transitions obtained from a (p, n)-type charge-exchange reaction on a target nucleus with T z = 1 with those from the β-decay of the T z = - 1 nucleus. The A = 58 system is the heaviest for which such a comparison is possible. As a part of the symmetry study, we measured the GT transitions from 58Ni (T z = 1) to 58Cu (T z = 0) by using the zero-degree (3 He, t) reaction at 150 MeV/nucleon. With the achieved resolution of 50 keV, many hitherto unresolved GT states have been identified. The GT transition strengths were obtained for states up to 8 MeV excitation, i.e., near to the Q window limitation ( Q EC = 9.37 MeV) of the β-decay from 58Zn (T z = - 1) to 58Cu. The strength distribution is compared with that from shell-model calculations.

Assuming isospin T is a good quantum number, the analog states of the low-lying states in T z = ′ (T 0 +1) nuclei can be found as excited T 0 +1 states in T z = ′T 0 nuclei. Therefore, if To + 1 states are identified in theexcited region of T z = ′T 0 nuclei, the structure of unstable nuclei with T z = ′(T 0 + 1) can be deduced. We measured and compared the transition strengths to pairs of excited analog states in inelastic and charge-exchange reactions on the same target nucleus. The T values of these analog states were identified by using the fact that the transition strengths to them are different depending on T. The identification of T = ½ and 3/2 nature of analog M1 and GT states in the mirror nuclei pair 2 7 Al and 2 7 Si is reported by comparing the transition strengths in high-resolution 2 7 Al(p,p') and 2 7 Al( 3 He, t) 2 7 Si reactions at 0°. The identified T = 3/2 states are analogous to the low-lying states of 2 7 Mg, which plays an important role in rp-process of nucleosynthesis.

Precise reaction cross sections (${\ensuremath{\sigma}}_{R}$) for $^{24\ensuremath{-}38}\mathrm{Mg}$ on C targets at energies around 240 MeV/nucleon have been measured at the Radioactive Isotope Beam Factory at RIKEN. The ${\ensuremath{\sigma}}_{R}$ for $^{36\ensuremath{-}38}\mathrm{Mg}$ have been measured for the first time. An enhancement of ${\ensuremath{\sigma}}_{R}$ compared to the systematics for spherical stable nuclei has been observed, especially in the neutron-rich region, which reflects the deformation of those isotopes. In the vicinity of the drip line the ${\ensuremath{\sigma}}_{R}$ for $^{37}\mathrm{Mg}$ is especially large. It is shown by analysis using a recently developed theoretical method that this prominent enhancement of ${\ensuremath{\sigma}}_{R}$ for $^{37}\mathrm{Mg}$ should come from the $p$-orbital halo formation breaking the $N=28$ shell gap.

The total charge-changing, charge pick-up, and partial charge-changing cross sections of very neutron-rich nuclei (Ne-30, Na-32,Na-33) with a proton target have been measured at similar to 240A MeV for the first time. We introduced the phenomenological correction factor in Glauber-model calculations for the total charge-changing cross sections with the proton target, and applied it to deduce the proton radii of these nuclei. For 30Ne and Na-32, the neutron skin thicknesses of the nuclei were deduced by comparing the proton radii with the matter radii deduced from the interaction cross-section measurements. A significant thick neutron-skin has been observed for the nuclei. We also found that the charge pick-up cross sections are much larger than those in the systematics of stable nuclei.

Y. Fujita et al. ; 5 pags. ; 3 figs. PACS numbers: 24.30.Cz, 25.55.Kr, 27.40.+z, Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A=42, 46, 50, and 54 >f-shell> nuclei in (He3, t) charge-exchange reactions. In the Ca42→Sc42 reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the Fe54→Co54 reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei. © 2014 American Physical Society., This work was in part supported by MEXT, Japan (Grants No. 13002001, No. 15540274, and No. 18540270); MICINN, Spain (Grant No. FPA200806419-C02-01). Y. F. and B. R. acknowledge the support of the Japan-Spain collaboration program by JSPS and CSIC.

Interaction cross sections have been measured for spin-aligned nuclear beams of deformed nucleus. The spin-aligned nuclear beams were created by selecting the momentum of fragments produced in the projectile fragmentation of intermediate energy heavy-ion beams. The directional correlation of nuclear reaction probability for heavy-ion beams of deformed nucleus has been directly observed for the first time.

Reaction cross sections ( σ R ) for 11Be and 8B on proton targets at 50 A ∼ 120 A MeV have been measured to distinguish between the proton- and neutron- density distributions at the nuclear surface. The σ R is connected with the nucleon density distributions by the Glauber theory. Since the nucleon-nucleon total cross sections in that energy region have a large isospin dependence, the σ R on proton targets should have a large difference between the proton and neutron in the halo structure. The experimental σ R on proton targets are in good agreement with the calculated ones assuming that the tail dominantly consists of a neutron for 11Be and a proton for 8B.

The magnetic dipole (μ) and electric quadrupole (Q) moments of short-lived nucleus 22F ( I π = 4 + , T 1 / 2 = 4.2 s ) have been measured for the first time by means of the β-NMR technique. A spin polarized 22F beam was produced through the charge exchange reaction of 22Ne and was implanted into single crysltals of NaF and MgF2 for μ and Q measurements, respectively. As a result, | μ ( F 22 ) | = ( 2.69443 ± 0.00039 ) μ N and | Q ( F 22 ) | = ( 3 ± 2 ) mb was obtained. These values are well reproduced by the shell model calculations.

25th International Nuclear Physics Conference, Florence, Italy, 2 Jun 2013 - 7 Jun 2013; The European physical journal / Web of Conferences Web of Conferences : proceedings proceedings 66, 02101 (2014). doi:10.1051/epjconf/20146602101, Published by EDP Sciences, Les Ulis

25th International Nuclear Physics Conference, Florence, Italy, 2 Jun 2013 - 7 Jun 2013; The European physical journal / Web of Conferences Web of Conferences : proceedings proceedings 66, 03084 (2014). doi:10.1051/epjconf/20146603084, Published by EDP Sciences, Les Ulis

Electric dipole (E1) reduced transition probability B(E1) of 90Zr was obtained by the inelastic proton scattering near 0 degrees using a 295 MeV proton beam and multipole decomposition analysis of the angular distribution by the distorted-wave Born approximation with the Hartree-Fock plus random-phase approximation model and inclusion of El Coulomb excitation, and the E1 strength of the pygmy dipole resonance was found in the vicinity of the neutron threshold in the low-energy tail of the giant dipole resonance. Using the data, we plan to determine the precise dipole polarizability αD which is defined as an inversely energy-weighted sum value of the elecrric dipole strength. The dipole polarizability is expected to constrain the symmetry energy term of the neutron matter equation of state. Thus systematical measurement of the dipole polarizability is important.

In this work we have studied ${T}_{z}=+2\ensuremath{\rightarrow}+1$, Gamow-Teller (GT) transitions in the $^{48}\mathrm{Ti}(^{3}\mathrm{He},t)^{48}\mathrm{V}$ charge-exchange reaction at 140 MeV/nucleon and ${0}^{\ensuremath{\circ}}$ at the Research Center for Nuclear Physics, Osaka. From the high-resolution facility, consisting of a high-dispersion beamline and the Grand Raiden spectrometer, the spectrum had an energy resolution of 21 keV, among the best achieved. Individual GT transitions were observed and GT strength was derived for each state populated up to an excitation energy of 12 MeV. The total sum of the $B$(GT) strength observed in discrete states was 4.0, which is 33% of the sum-rule-limit value of 12. The results were compared with the results of shell-model calculations carried out with the GXPF1J interaction. The measured $B$(GT) distribution was also compared with that obtained in the $(^{3}\mathrm{He},t)$ charge-exchange reaction on $^{47}\mathrm{Ti}$. On the assumption of isospin symmetry the $\ensuremath{\beta}$ spectrum of the ${T}_{z}=\ensuremath{-}2$ nucleus $^{48}\mathrm{Fe}$ was deduced from the observed spectrum in the $^{48}\mathrm{Ti}(^{3}\mathrm{He},t)^{48}\mathrm{V}$ reaction and this predicted spectrum was compared with the measured one.

Motivated by the need of spectroscopic data to better understand the astrophysical rp-process, we developed a new experimental method using the Grand Raiden magnet spectrometer to study protin rich nuclei with α and 3 He induced reactions. First results of the 24 Mg( 4 He, 6 He) 22 Mg reaction at 206 MeV and 0° are presented, showing states relevant for resonant reaction rate calculations of the proton capture 21 Na(p,γ) 22 Mg and the 18 Ne(α,p) 21 Na reaction which controls the break-out of the hot CNO cycles at X-ray burst conditions.

A high-resolution measurement of inelastic proton scattering off $^{90}\mathrm{Zr}$ near 0\ifmmode^\circ\else\textdegree\fi{} was performed at 295 MeV with a focus on a pronounced strength previously reported in the low-energy tail of giant dipole resonance. A forest of fine structure was observed in the excitation energy region 7--12 MeV. A multipole decomposition analysis of the angular distribution for the forest was carried out using the ECIS95 distorted-wave Born approximation code with the Hartree-Fock plus random-phase approximation model of $E1$ and $M1$ transition densities and inclusion of $E1$ Coulomb excitation. The analysis separated pygmy dipole and $M1$ resonances in the forest at ${E}_{\mathrm{PDR}}=9.15\ifmmode\pm\else\textpm\fi{}0.18\text{ }\text{ }\mathrm{MeV}$ with ${\ensuremath{\Gamma}}_{\mathrm{PDR}}=2.91\ifmmode\pm\else\textpm\fi{}0.64\text{ }\text{ }\mathrm{MeV}$ and at ${E}_{M1}=9.53\ifmmode\pm\else\textpm\fi{}0.06\text{ }\text{ }\mathrm{MeV}$ with ${\ensuremath{\Gamma}}_{M1}=2.70\ifmmode\pm\else\textpm\fi{}0.17\text{ }\text{ }\mathrm{MeV}$ in the Lorentzian function, respectively. The $B(E1)\ensuremath{\uparrow}$ value for pygmy dipole resonance over 7--11 MeV is $0.75\ifmmode\pm\else\textpm\fi{}0.08\text{ }\text{ }{e}^{2}\text{ }{\mathrm{fm}}^{2}$, which corresponds to $2.1\ifmmode\pm\else\textpm\fi{}0.2%$ of the Thomas-Reiche-Kuhn sum rule.

Scattering of protons of several hundred MeV is a promising new spectroscopic tool for the study of electric dipole strength in nuclei. A case study of 208Pb shows that at very forward angles J^pi = 1- states are strongly populated via Coulomb excitation. A separation from nuclear excitation of other modes is achieved by a multipole decomposition analysis of the experimental cross sections based on theoretical angular distributions calculated within the quasiparticle-phonon model. The B(E1) transition strength distribution is extracted for excitation energies up to 9 MeV, i.e., in the region of the so-called pygmy dipole resonance (PDR). The Coulomb-nuclear interference shows sensitivity to the underlying structure of the E1 transitions, which allows for the first time an experimental extraction of the electromagnetic transition strength and the energy centroid of the PDR., Comment: submitted to Phys. Rev. C

The Gamow-Teller transition strengths, $B$(GT), in $pf$-shell nuclei are of interest in nuclear physics as well as in nuclear astrophysics. A high-resolution (${}^{3}\mathrm{He},t$) charge-exchange (CE) reaction was performed on the ${T}_{z}=+1$ nucleus ${}^{54}$Fe at 0${}^{\ensuremath{\circ}}$ and at an intermediate incident energy of 140 MeV/nucleon for the study of precise GT transition strengths to the final ${T}_{z}=0$ nucleus ${}^{54}$Co. By applying dispersion matching techniques for a high-quality ${}^{3}$He beam at RCNP, an energy resolution of 21 keV and an angular resolution of 5 mr were realized. The bumplike structure of the GT resonance observed in low-resolution CE reactions at around the excitation energy (${E}_{x}$) of 10 MeV was resolved in individual $L$ $=$ 0, GT states. Excitation strengths were obtained for these GT states. If the ${R}^{2}$ value that is defined by the ratio between GT and Fermi unit cross sections is known, the $B$(GT) values can be determined from the excitation strengths. For the derivation of the ${R}^{2}$ value, the ``merged analysis'' combining the GT strength distribution from the ${}^{54}$Fe(${}^{3}\mathrm{He},t$)${}^{54}$Co study and the half-life from a ${}^{54}$Ni $\ensuremath{\beta}$ decay was used, where $T=1$ isospin symmetry for $A=54$ isobars was assumed. The GT strengths were compared with a shell-model calculation using the GXPF1 interaction. The final GT states can have the isospin values $T$ $=$ 0, 1, and 2. The isospin $T$ of each GT state observed in the $8.3\ensuremath{\le}{E}_{x}\ensuremath{\le}12.0$ MeV region of the ${}^{54}$Fe(${}^{3}\mathrm{He},t$)${}^{54}$Co spectrum was identified by comparing the excitation strength with that of corresponding $M1$ state observed in a ${}^{54}$Fe($p,{p}^{\ensuremath{'}}$)${}^{54}$Fe experiment. The $B$(GT) values of the states identified to have $T=2$, in particular, are of importance for the calculation of the electron capture rates at the core-collapse stage of presupernovae. The $B$(GT) strengths were further compared with $B(M1)$ strengths measured in the ${}^{54}$Fe($e,{e}^{\ensuremath{'}}$)${}^{54}$Fe reaction. In the $M1$ excitation using an electromagnetic probe, isoscalar (IS) and isovector (IV) orbital type operators are active in addition to the IV spin type operator that mediates the GT transitions. The contributions of the IS and IV orbital terms were studied by calculating the ratio of the strengths of analogous $M1$ and GT transitions.

The rise time of stellar x-ray bursts is a signature of thermonuclear runaway processes in the atmosphere of neutron stars and is highly sensitive to a series of ($\ensuremath{\alpha}$,$p$) reactions via high-lying resonances in $sd$-shell nuclei. Lacking data for the relevant resonance levels, the stellar reaction rates have been calculated using statistical, Hauser-Feshbach models, assuming a high-level density. This assumption may not be correct in view of the selectivity of the ($\ensuremath{\alpha}$,$p$) reaction to natural parity states. We measured the ${}^{28}$Si($p$,$t$)${}^{26}$Si reaction with a high-resolution spectrometer to identify resonance levels in ${}^{26}$Si above the $\ensuremath{\alpha}$-emission threshold at 9.164 MeV excitation energy. These resonance levels are used to calculate the stellar reaction rate of the ${}^{22}$Mg($\ensuremath{\alpha}$,$p$)${}^{25}$Al reaction and to test the validity of the statistical assumption.

A benchmark experiment on Pb-208 shows that polarized proton inelastic scattering at very forward angles including 0 degrees is a powerful tool for high-resolution studies of electric dipole (E1) and spin magnetic dipole (M1) modes in nuclei over a broad excitation energy range to test up-to-date nuclear models. The extracted E1 polarizability leads to a neutron skin thickness r(skin) = 0.156(-0.021)(+0.025) fm in Pb-208 derived within a mean-field model [Phys. Rev. C 81, 051303 (2010)], thereby constraining the symmetry energy and its density dependence relevant to the description of neutron stars.

A high-energy-resolution $^{9}\mathrm{Be}$($^{3}\mathrm{He}$,$t$)$^{9}\mathrm{B}$ charge-exchange reaction was performed around a scattering angle of ${0}^{\ifmmode^\circ\else\textdegree\fi{}}$ and at an intermediate incident energy of 140 MeV/nucleon for the study of precise Gamow-Teller (GT) transition strengths. The energy resolution of 30 keV allowed a precise deconvolution of the spectrum and the determination of angular distributions of cross sections, excitation energies, and decay widths. The GT strength of 10 states has been determined for the first time using the GT strength of the analogous $\ensuremath{\beta}$ decays of $^{9}\mathrm{Li}$ and $^{9}\mathrm{C}$ as standards. The large difference between the GT strengths going to the low-lying $T=1/2$ and the highly excited $T=3/2$ states is interpreted as a result of their different spatial structures. The obtained GT strength distribution is compared to the results of a ($p$,$n$) experiment with lower resolution performed in the 1980s. In particular, the width of the 16.8 MeV, ${J}^{\ensuremath{\pi}}=(5/{2}^{+}$) state has been determined for the first time.

The {sup 150}Nd({sup 3}He,t) reaction at 140 MeV/u and {sup 150}Sm(t,{sup 3}He) reaction at 115 MeV/u were measured, populating excited states in {sup 150}Pm. The transitions studied populate intermediate states of importance for the (neutrinoless) {beta}{beta} decay of {sup 150}Nd to {sup 150}Sm. Monopole and dipole contributions to the measured excitation-energy spectra were extracted by using multipole decomposition analyses. The experimental results were compared with theoretical calculations obtained within the framework of the quasiparticle random-phase approximation, which is one of the main methods employed for estimating the half-life of the neutrinoless {beta}{beta} decay (0{nu}{beta}{beta}) of {sup 150}Nd. The present results thus provide useful information on the neutrino responses for evaluating the 0{nu}{beta}{beta} and 2{nu}{beta}{beta} matrix elements. The 2{nu}{beta}{beta} matrix element calculated from the Gamow-Teller transitions through the lowest 1{sup +} state in the intermediate nucleus is maximally about half that deduced from the half-life measured in 2{nu}{beta}{beta} direct counting experiments, and at least several transitions through 1{sup +} intermediate states in {sup 150}Pm are required to explain the 2{nu}{beta}{beta} half-life. Because Gamow-Teller transitions in the {sup 150}Sm(t,{sup 3}He) experiment are strongly Pauli blocked, the extraction of Gamow-Teller strengths was complicated by the excitation of the 2({h_bar}/2{pi}){omega}, {Delta}L=0, {Delta}S=1 isovector spin-flipmore » giant monopole resonance (IVSGMR). However, the near absence of Gamow-Teller transition strength made it possible to cleanly identify this resonance, and the strength observed is consistent with the full exhaustion of the non-energy-weighted sum rule for the IVSGMR.« less

The proportionality between differential cross sections at vanishing linear momentum transfer and Gamow-Teller transition strength, expressed in terms of the unit cross section (${\mathrm{\ensuremath{\sigma}\ifmmode \hat{}\else \^{}\fi{}}}_{\mathit{GT}}$), was studied as a function of target mass number for ($t$,$^{3}\mathrm{He}$) and ($^{3}\mathrm{He}$,$t$) reactions at $115A$ MeV and $140A$ MeV, respectively. Existing ($^{3}\mathrm{He}$,$t$) and ($t$,$^{3}\mathrm{He}$) data on targets with mass number $12\ensuremath{\leqslant}A\ensuremath{\leqslant}120$ were complemented with new and reevaluated ($t$,$^{3}\mathrm{He}$) data on proton, deuteron, $^{6}\mathrm{Li}$, and $^{12}\mathrm{C}$ targets. It was found that in spite of the small difference in beam energies between the two probes, the unit cross sections have a nearly identical and simple dependence on target mass number $A$, for $A\ensuremath{\geqslant}12$: ${\mathrm{\ensuremath{\sigma}\ifmmode \hat{}\else \^{}\fi{}}}_{\mathit{GT}}=109/{A}^{0.65}$. The factorization of the unit cross sections in terms of a kinematical factor, a distortion factor, and the strength of the effective spin-isospin transfer nucleus-nucleus interaction was investigated. Simple phenomenological functions depending on mass number $A$ were extracted for the latter two. By comparison with plane and distorted-wave Born approximation calculations, it was found that the use of a short-range approximation for knock-on exchange contributions to the transition amplitude results in overestimated cross sections for reactions involving the composite ($^{3}\mathrm{He}$,$t$) and ($t$,$^{3}\mathrm{He}$) probes.

Since the identification of ongoing Al-26 production in the universe, the reaction sequence Mg-24(p,gamma)Al-25(beta(+)nu)Mg-25(p,gamma)Al-26 has been studied intensively. At temperatures where the radiative capture on Al-25 (t(1/2) = 7.2 s) becomes faster than the beta(+) decay, the production of Al-26 can be reduced due to the depletion of Al-25. To determine the resonances relevant for the Al-25(p,gamma) Si-26 bypass reaction, we measured the Si-28(p,t)Si-26 reaction with high-energy precision using the Grand Raiden spectrometer at the Research Center for Nuclear Physics, Osaka. Several new energy levels were found above the p threshold and for known states excitation energies were determined with smaller uncertainties. The calculated stellar rates of the bypass reaction agree well with previous results, suggesting that these rates are well established.

We report on the first successful extraction of a ${\ensuremath{\beta}}^{+}$ Gamow-Teller strength distribution from a radioactive isotope in an intermediate-energy charge-exchange experiment in inverse kinematics. The ($^{7}\mathrm{Li},^{7}\mathrm{Be}+\ensuremath{\gamma}(429\text{ }\text{ }\mathrm{keV})$) reaction at $100A\text{ }\text{ }\mathrm{MeV}$ was used to measure Gamow-Teller transition strengths from $^{34}\mathrm{P}$ to states in $^{34}\mathrm{Si}$. The results show that little mixing occurs between $sd$ and $pf$ shell configurations for the low-lying ${0}^{+}$ and ${2}^{+}$ states even though $^{34}\mathrm{Si}$ neighbors the island of inversion and low-lying $2\ensuremath{\hbar}\ensuremath{\omega}$ intruder states exist. Shell-model calculations in the $sdpf$ model space are consistent with these findings.

The Gamow‐Teller (GT) transitions in the β+ (electron capture) direction from the ground state of 56Fe to the excited states of 56Mn play an important role in the core collapse of presupernova. Assuming that isospin analogous transitions in isobars have corresponding strengths, we deduced these GT strengths by combining the results of the 56Fe(p, p′)56Fe experiment performed at 200 MeV and 0° and the 56Fe(3He, t)56Co experiment in the ββ direction at 140 MeV/u and 0°. The ground state of 56Fe has the isospin value of T = 2, while the GT states in 56Mn have T = 3. In order to identify the analogous T = 2→3, GT transitions in the 56Fe(p, p′)56Fe and the 56Fe(3He, t)56Co measurements, we used the fact that the isospin Clebsch‐Gordan (CG) coefficients for these T = 2→3 transitions are different in these measurements. Then the GT transition strengths B(GT) in the β+ direction can be deduced from the B(GT) values of the corresponding transitions well determined in the 56Fe(3He, t)56Co measurement assuming the i...

Reaction cross sections for stable nuclei at intermediate energies have been measured precisely and systematically. The data have been found to be reproduced nicely by the optical‐limit approximation of Glauber theory modified to include the nucleon multiple scattering effect and the Fermi‐motion effect. Applying this prescription, the nucleon density distribution of 17Ne has been studied. The surface structure of 8B and 11Be has been also studied using this prescription and hydrogen targets. Using the RIBF that has just started application to studies of exotic nuclei, neutron‐rich Ne isotopes around the Island of Inversion have been investigated through measurements of their interaction cross sections.

The rp‐process nucleosynthesis proceeds through nuclei near the proton drip‐line, in which Gamow‐Teller (GT) transitions starting from unstable pf‐shell nuclei play important roles. In the β‐decay study of these nuclei, half‐lives can be measured rather accurately. On the other hand, in the high‐resolution (3He, t) charge‐exchange reactions on mirror nuclei, individual GT transitions can be studied up to high excitations. For the accurate study of the GT transition strengths in the A = 52, T = 2, system, we compare and combine the β‐decay study of the proton‐rich nucleus 52Ni and the 52Cr(3He, t) measurement assuming the isospin symmetry of the Tz = ±2→±1 transitions.