Y. Ando

Quadrupole deformation of 12Be studied by proton inelastic scattering

Abstract Inelastic proton scattering exciting the 2 + 1 states in the neutron-rich beryllium isotopes 10,12 Be has been studied in inverse kinematics. From a coupled-channel analysis, the deformation lengths for the 2 + 1 states in 10 Be and 12 Be were determined to be 1.80±0.25 fm and 2.00±0.23 fm respectively, indicating that a tendency towards strong quadrupole deformation is preserved for these nuclei and that the singly-closed shell structure does not prevail in 12 Be. A quantitative analysis based on shell model calculations supports this picture.

Determination of the astrophysical 13N (p, γ) 14O cross section through the Coulomb dissociation method☆

Abstract The Coulomb dissociation reaction 208Pb(14O, 13N p)208Pb was measured at Ein = 87.5 MeV/u to determine the radiative width Γγ of the 1− state in 14O at Eex = 5.17 MeV. This state dominates the radiative capture process 13N(p, γ) 14O, a key reaction in the hot CNO cycle of hydrogen burning in stars. We have deduced Γγ = 3.1 ± 0.6 eV with the help of a coupled channel calculation. The validity of the technique was confirmed in the case of the 208Pb(13N, 12C p)208Pb reaction exciting the 1 2 + state in 13N whose width is known.

Coulomb excitation of 11Be

Abstract The Coulomb excitation of a halo nucleus 11 Be to its first bound excited state (E1: 1 2 + → 1 2 − ) has been studied using a 64 MeV/u 11 Be radioactive beam incident on a 208 Pb target. The electric dipole strength deduced by a first-order perturbation analysis is in good agreement with the result of previous life-time measurements of the 11 Be 1 2 − state.

Isobaric analog state of 11Li

The isobaric analog state (IAS) of the halo nucleus 11Li has been investigated using the charge exchange reaction 11Li(p,n)11Be∗ in inverse kinematics at E(11Li) = 64A MeV. The IAS was observed in 11Be, for the first time, at an excitation energy of 21.16 ± 0.02 MeV with a width of 0.49 ± 0.07 MeV (FWHM). The unit cross section, distortion factor and effective N-N interaction associated with the Fermi transition are extracted. Coulomb displacement energy, decay width, reaction variables and their relation to the halo structure are discussed.

Response of BaF2, BaF2-plastic, and BGO scintillators to neutrons with energies between 15 and 45 MeV

The response of BaF2, BaF2-plastics (BPS), and BGO scintillators to neutrons was studied in the energy range En = 15 to 45 MeV. The detection efficiencies of the BaF2 and BGO scintillators become large with increasing neutron energy, whereas the one of the0 BPS shows a weak energy dependence. Around En = 45 MeV, these scintillators have about the same efficiencies (per unit thickness) as that of the NE213 liquid scintillator.

Study of the 7Be(p, γ)8B Reaction with the Coulomb Dissociation Method

The Coulomb-dissociation cross section for the process B-8 --> Be-7 + p in the field of Pb-208 was measured at E(B-8) = 46.5 A MeV. The Be-7(p,gamma)B-8 cross section relevant to the high-energy B-8 solar-neutrino production was extracted at E(C.M.) = 0.6 - 1.7 MeV. Two theoretical models on the structure of 8B were used to evaluate possible corrections due to M1 and E2 admixtures to the dominant E1 cross sections. Their overall effect is shown to be small regardless of the choice of the models. The present result is consistent with the results of the direct measurements of Filippone et al. and Vaughn et al. within errors. This result suggests further studies with the Coulomb-dissociation method to extract astrophysical S-17 factor at similar to 20 keV relevant to the high-energy solar-neutrino flux.

Isobaric analog state of 14Be

The halo structure of the neutron-dripline nucleus 14Be has been investigated by various approaches, such as the interaction cross section measurement, dissociation reaction and 14Be fragmentation. In the recent plausible view, the mixing of s and d-wave components in the halo wave function has been suggested. In the present study, the halo structure of 14Be was investigated by measuring its Isobaric Analog State (IAS). Since the wave function of the IAS is essentially the same as that of its isobaric partner, possible exotic natures of 14Be may be traced in properties of the IAS such as the Coulomb displacement energy (ΔE C) and the width of the IAS. The IAS of the 14Be was excited by the charge-exchange reaction which was successfully applied to the neutron-dripline nucleus 11Li and obtained the halo properties [1, 2]. In the present study, applying this reaction to 14Be, we have measured the 14Be(p,n)14B* reaction in inverse kinematics at E in = 74 A MeV [3].

Molecular states in neutron-rich beryllium isotopes

Excited states in 1 2 Be and 1 4 Be were studied by using an exotic beam of 1 4 Be at 75 A MeV. A new excited state in 1 2 Be was observed at 11.8 MeV. The angular-correlation analysis showed that the spin for the new level is tentatively assigned to be 0. According to the energy-spin systematics, the observed state may be a member of the rotational band of the 6 He- 6 He cluster structure. Three excited states in 1 4 Be were also found at 10.8 MeV, 11.6 MeV, and 15.5 MeV.

Inelastic Scattering of 12Be with 4He

. Inelastic scattering of the neutron-rich nucleus 1 2 Be on a liquid-He target has been studied by measuring de-excitation γ rays in coincidence with scattered 1 2 Be. In the angular distribution, a difference between the 2 + 1 and the 1- state in 1 2 Be was cleary seen.

Coulomb Excitation of 24Si

We have measured Coulomb excitation of 2 4 Si to its first excited state to obtain the E2 transition probability. This is the first measurement of B(E2) for a T z = -2 nucleus, which enables us to compare their transitionprobabilities between the mirror pair of T = 2, namely 2 4 Si and 2 4 Ne.