Author/Authors :
E. Tryggestad، نويسنده , , T Aumann، نويسنده , , T Baumann، نويسنده , , D Bazin، نويسنده , , J.R. Beene، نويسنده , , Y Blumenfeld، نويسنده , , B.A. Brown، نويسنده , , M Chartier، نويسنده , , M.L. Halbert، نويسنده , , P Heckman، نويسنده , , J.F. Liang، نويسنده , , D.C. Radford، نويسنده , , D Shapira، نويسنده , , M Thoennessen، نويسنده , , R.L. Varner Jr.، نويسنده ,
Abstract :
Two 1− levels at 5.35(10) and 6.85(5) MeV were observed for the first time in 20O. The strong direct excitation and subsequent γ-ray decay of these states in virtual photon scattering at 100 MeV/nucleon, along with B(Eλ) predictions for 20O states in this energy region, established their dipole character. The extracted B(E1)↑ values of ≃0.062(16) e2 fm2 and ≃0.035(9) e2 fm2 for the 5.35 and 6.85 MeV states, respectively, are significantly larger than shell model calculations predict. Such large dipole strengths are not observed for low-lying 1− states in 18O, indicating a shift of dipole strength towards lower energies as one approaches the neutron drip-line.
Keywords :
1? levels of 20O , Coulomb excitation of 18O , Coulomb excitation of 20O , Virtual photon scattering on 18O , Virtual photon scattering on 20O
