Search

The alpha inelastic scattering from Mg was measured to obtain the isoscalar natural-parity excitation strengths and to search for the α-condensed states. The multipole decomposition analysis for the measured cross sections was performed. The strength distributions for the Δ L = 0-3 were successfully obtained and the possible candidates for the α-condensed states around the O core were found. [ABSTRACT FROM AUTHOR]

Spectroscopy for neutron-rich nuclei He and Be has been performed by means of heavy-ion double charge exchange (HIDCX) (O, Ne) reaction on stable target nuclei Be and C, respectively. Several clear peaks in Be at low excitation energy region even above neutron separation energy have been observed in one-shot measurement, whereas no prominent signals of He have been observed owing to the small cross section. It is shown that the HIDCX reaction is a new powerful spectroscopic tool for study of unstable neutron-rich nuclei. [ABSTRACT FROM AUTHOR]

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 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 $3/2^-_3$ state at Ex = 8.56 MeV is well described by the AMD calculation and is an evidence for a developed 2α + t cluster structure. [ABSTRACT FROM AUTHOR]

The 12C excitation energy spectra populated in both proton and α-particle inelastic scattering measurements are examined. The data indicate the existence of a 2+ state at Ex = 9.75(0.15) MeV with a width of 750(150) keV. It is believed that this state corresponds to the 2+ excitation of the 7.65 MeV, 0+, Hoyle state, which acts as the main path by which carbon is synthesized in stars. A simultaneous Ä-matrix analysis of the two sets of data indicates that the 2+ state possesses a very large α-reduced width, approaching the Wigner limit. This would indicate that the state is associated with a highly clustered structure. The potential geometric arrangements of the clusters is discussed. [ABSTRACT FROM AUTHOR]

We have studied gas-like states of α clusters around an 16O core in 24Mg based on a microscopic α-cluster model. The 0+ states below the 16O + α + α threshold, which are candidates for the resonance solution judging from the energy convergence behavior, are strongly excited by an isoscalar monopole (E0) operator from the ground state, which could be observed as an experimental signature of well-developed α gas-like states in the excited states. These states have significant overlaps with the THSR (Tohsaki-Horiuchi-Schuck-Röpke) wave functions with large spatial extension. [ABSTRACT FROM AUTHOR]

Differential cross sections of isoscalar and isovector spin-M1 (P+ → 1+) transitions are measured using high-energy-resolution proton inelastic scattering at Ep = 295 MeV on 24Mg, 28Si, 32S, and 36Ar at 0°-l 4°. 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 Ex = 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. [ABSTRACT FROM AUTHOR]

Background: The 14O(α,p) 17F reaction plays an important role as the trigger reaction for the x-ray burst. Purpose: The direct measurement of 14O(α,p) 17F was made for studying the resonant states in 18Ne and determining the reaction rate of 14O(α,p) 17F at astrophysical temperatures. Methods: The differential cross section of the 14O(α,p) 17F reaction was measured using a 2.5-MeV/u 14O radioactive beam and the thick target method in inverse kinematics. Three sets of ΔE-E Si telescopes were installed and coincidence measurements were performed. We analyzed single-proton decay events using the time-of-flight (TOF) information of the recoiling protons. Results: The excitation function of 14O(α,p) 17F was acquired for excitation energies between 7.2 and 10.4 MeV in 18Ne by considering the two channels which decay to the ground state and first excited state of 17F. Several new, as well as previously known, states in 18Ne were observed and their resonance parameters were extracted from R-matrix analysis. The contributions of four resonances over the excitation energy range, 7 < Ex < 8.2 MeV, to the 14O(α,p) 17F reaction rate were calculated. Conclusions: We observed very strong single-proton decay events, but did not observe strong double-proton decay events as in a previous study by Fu et al. The reaction rates contributed by the 7.35-, 7.58-, and 7.72-MeV states were estimated to be dominant at temperatures T9 > 2. Among these three states, the 7.35-MeV state was found to enhance the reaction rate by a factor of 10 greater than the other two resonance states. [ABSTRACT FROM AUTHOR]

The excitation of the isoscalar giant monopole resonance (ISGMR) in 208Pb and 116Sn has been investigated using small-angle (including 0°) inelastic scattering of 100 MeV/u deuteron and multipole-decomposition analysis (MDA). The extracted strength distributions agree well with those from inelastic scattering of 100 MeV/u α particles. These measurements establish deuteron inelastic scattering at Ed -100 MeV/uas a suitable probe for extraction of the ISGMR strength with MDA, making feasible the investigation of this resonance in radioactive isotopes in inverse kinematics. [ABSTRACT FROM AUTHOR]

Background: The resonance structure in 11C is of particular interest with regard to the astrophysical 7Be(α,γ) reaction, relevant at high temperature, and to the α-cluster structure in 11C. Purpose: The measurement was made to determine the unknown resonance parameters for the high excited states of 11C. In particular, the α-decay width can be useful information to discuss the α-cluster structure in 11C. Methods: New measurements of 7Be+α resonant scattering and the 7Be(α,p)10B reaction in inverse kinematics were performed for center-of-mass energy up to 5.5 MeV, and the resonances at excitation energies of 8.9-12.7 MeV in the compound 11C nucleus were studied. Inelastic scattering of 7Be+α and the 7Be(α,p1)10B* reaction were also studied with a simultaneous γ-ray measurement. The measurements were performed at the low-energy radioactive ion beam facility CRIB (CNS Radioactive Ion Beam separator) of the Center for Nuclear Study, the University of Tokyo. Results: We obtained excitation functions of 7Be(α,α0)7Be (elastic scattering), 7Be(α,α1)7Be* (inelastic scattering), 7Be(α,p0)10B, and 7Be(α,p1)10B*. Many resonances including a new one were observed and their parameters were determined by using an R-matrix analysis. Conclusions: The resonances we observed possibly enhance the 7Be(α,γ) reaction rate but with a smaller magnitude than the lower-lying resonances. A new negative-parity cluster band, similar to the one previously suggested in the mirror nucleus 11B, is proposed. [ABSTRACT FROM AUTHOR]

A high-resolution measurement of inelastic proton scattering off 90Zr near 0° 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 EPDR = 9.15 ± 0.18 MeV with &Ggr;PDR = 2.91 ± 0.64 MeV and at Em1 = 9.53 ± 0.06 MeV with &Ggr;Μ1 = 2.70 ± 0.17 MeV in the Lorentzian function, respectively. The B(E1) &Uarr; value for pygmy dipole resonance over 7-11 MeV is 0.75 ± 0.08 e2fm2, which corresponds to 2.1 ± 0.2% of the Thomas-Reiche-Kuhn sum rule. [ABSTRACT FROM AUTHOR]

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, Jπ = 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(El) transition strength distribution is extracted for excitation energies up to 9 MeV; that is, in the region of the so-called pygmy dipole resonance (PDR). The Coulomb-nuclear interference shows sensitivity to the underlying structure of the £ 1 transitions, which allows for the first time an experimental extraction of the electromagnetic transition strength and the energy centroid of the PDR. [ABSTRACT FROM AUTHOR]

A new measurement of α resonant scattering on 7Li was performed over the excitation energy of 10.2-13.0 MeV in 11B at the low-energy RI beam facility CNS Radioactive Ion Beam separator (CRIB) of the Center for Nuclear Study (CNS), University of Tokyo. The excitation function of 7Li+α at 180° in the center-of-mass system was successfully measured for the first time with the inverse kinematics method, providing important information on the α cluster structure in 11B and the reaction rate of 7Li(α,γ), which is relevant to the 11B production in the ? process in core-collapse supernovae. The excitation function of the 7Li(α,p) reaction cross section for 11.7-13.1 MeV was also measured. [ABSTRACT FROM AUTHOR]

The excitation and subsequent decay by proton emission of the isovector spin-flip giant monopole resonance are studied via the 208Pb(3He,t) reaction at 410 MeV. In the triton-singles spectrum 60 ± 5% of the non-energy-weighted sum-rule strength for this 2h̵ω resonance is found in the region 29 < Ex(208Bi) < 51 MeV. The central excitation energy and width of the IVSGMR are determined to be 37 ± 1 MeV and 14 ± 3 MeV, respectively. [Copyright &y& Elsevier]