Mineo Kurokawa

Large deformation of the very neutron-rich nucleus 32Mg from intermediate-energy Coulomb excitation

Abstract The Coulomb excitation of a very neutron-rich nucleus 32Mg to its 2+ state was studied using an unstable nuclear beam of 32Mg at 49.2 MeV/u with a 208Pb target. The B(E2) value of 454±78 e2fm4 was extracted by a coupled channel analysis. The value is in good agreement with recent predictions. It confirms a large deformation for 32Mg suggested by the low excitation energy of the 2+ state, and points to the vanishing of the N = 20 shell gap.

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.

New α-decaying neutron deficient isotopes197Rn and200Fr

New neutron-deficient isotopes,197Rn,197mRn, and200Fr have been produced and identified on the basis of genetic correlations in the166Er(36Ar,5n)197Rn (Elab=186, 200 MeV), and169Tm(36Ar,5n)200Fr (Elab=186 MeV) reactions. The evaporation residues were separated from the beam by using a gas-filled recoil separator and implanted onto a position-sensitive solid-state detector. The α-decay energies (half-lives) of197Rn,197mRn and200Fr have been determined to be 7261±30 keV (51−15+35 ms), 7370±30 keV (18−5+9ms), and 7500±3O keV, (570−140+270 ms), respectively.

Coulomb Dissociation ofB8and theBe7(p,γ)B8Reaction at Low Energies

The cross section for Coulomb dissociation of [sup 8]B---the [sup 208]Pb([sup 8]B,[sup 7]Be [ital p])[sup 208]Pb reaction---was measured using a [sup 8]B radioactive beam of 46.5 MeV/nucleon energy, and the cross section for the [sup 7]Be([ital p],[gamma])[sup 8]B capture reaction was deduced at low energies; [ital E][sub c.m.]=0.6[minus]1.7 MeV. The extracted astrophysical [ital S][sub 17] factors were found to be consistent with the values measured by Vaughn [ital et] [ital al]. and Filippone [ital et] [ital al]. This result encourages further experimental studies extended to lower relative energies for a new determination of the [ital S][sub 17] value relevant to the [sup 8]B solar neutrino flux.