Y. U. Matsuyama

Isomeric 0+ state in 12Be

An isomeric 0+ state at E x = 2.24 MeV in 12Be was found in the projectile fragmentation of 18O at 100 A MeV on a Be target. The excitation energy and the spin assignment were deduced by the measurements of the energies and the angular correlation function of the coincident two γ-rays corresponding to the 0+ → 2+ → 0+ decay, respectively.

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.

Low-lying proton intruder state in 13B

Abstract The neutron-rich nucleus 13 B was studied via the proton transfer reaction 4 He( 12 Be,  13 B γ ) at 50 A MeV . The known 4.83-MeV excited state was strongly populated and its spin and parity were assigned to 1 / 2 + by comparing the angular differential cross section data with DWBA calculations. This low-lying 1 / 2 + state is interpreted as a proton intruder state and indicates a deformation of the nucleus.

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.

Exotic cluster states in 12Be via α‐inelastic scattering

Excited states in the neutron‐rich nucleus 12Be were experimentally investigated via α‐inelastic scattering. The excited states in the 12Be nucleus were populated by a 12Be(α,α′) reaction at 60 A MeV in the inverse kinematics, and identified by measuring a 6He+6He breakup channel in coincidence. The differential cross section and the angular correlations between the decay particles were obtained for each excitation energy from 10 MeV to 20 MeV, reconstructed by the measured momentum vectors of the two 6He’s.A multipole decomposition analysis based on the distorted‐wave Born approximation was applied for the angular distribution of the inelastic scattering together with the angular correlation between the decay particles with respect to the directions of the incident beam and to the momentum transfer simultaneously. From the decomposed excitation energy spectra for L=0, 2, and 4, new excited states with Jπ=0+ and Jπ=2+ were identified, which were candidates of the band‐head of a largely deformed rotational...

Coulomb dissociation experiment for explosive hydrogen burning: Study of the 22Mg(p, γ)23Al reaction

By taking advantage of the high efficiency of the Coulomb dissociation method, we studied the stellar 22Mg(p, γ)23Al reaction. The radiative width Γγ of the first excited state in 23Al was determined by measuring the intermediate-energy 23Al → 22Mg + p breakup process with a lead target.

Investigation of Stellar 26Si(p,γ)27P Reaction via Coulomb Dissociation

The Coulomb dissociation of the proton-rich nuclei {sup 27}P was studied experimentally using {sup 27}P beams at 57 MeV/nucleon with a lead target. The radiative widths of the low-lying excited state in {sup 27}P were deduced. The resonant capture reaction rate of stellar {sup 26}Si(p,{gamma}){sup 27}P through these states was estimated using the measured radiative widths. The astrophysical implications obtained from the extracted reaction rate will be discussed.

Investigation of Stellar 26 Si (p,γ) 27 P Reaction via Coulomb Dissociation

The Coulomb dissociation of the proton-rich nuclei {sup 27}P was studied experimentally using {sup 27}P beams at 57 MeV/nucleon with a lead target. The radiative widths of the low-lying excited state in {sup 27}P were deduced. The resonant capture reaction rate of stellar {sup 26}Si(p,{gamma}){sup 27}P through these states was estimated using the measured radiative widths. The astrophysical implications obtained from the extracted reaction rate will be discussed.

Coulomb Dissociation of 27P for Study of 26Si(p,γ)27P Reaction

The Coulomb dissociation of the proton‐rich nuclei 27P was studied experimentally using a 27P beam at 57 MeV/nucleon with a lead target. The γ decay widths of the low‐lying excited states in 27P were deduced. The resonant capture reaction rate of stellar 26Si(p,γ)27P through these states was estimated using the measured γ decay width. The astrophysical implications derived from the estimated reaction rate is discussed.

Evolution of the N = 20 shell gap

Stucture of N = 17,18 nuclei has been investigated via proton inelastic scattering and neutron removal reactions up to the neutron dripline in inverse kinematics by use of radioctive ion beams provided by the RIKEN isotope separator, RIPS. Low energy excited states have been found in all the 26,27F and 27Ne nuclei, which are out of the neutron sd shell configuration space and are considered as intruder states arisng from cross shell excitations. Monte-Carlo shell model calculations with the sdpf-m interaction predict low energy negative parity excited states from neutron cross shell excitation at N = 17,18, which is in agreement with our experimental results. Observation of intruder states even at N = 17, especially the p3/2 state in 27Ne at 765 keV is a clear indication of a vanishing N = 20 shell gap at Z = 8 as predicted by the sdpf-m shell model calculations.