The double differential cross sections at lab between 0.0°and 12.3°and the polarization transfer D NN at 0°for the 90 Zr(p,n) reaction are measured at a bombarding energy of 295 MeV. A multipole decomposition technique is applied to the cross sections to extract Lϭ0, Lϭ1, Lϭ2, and Lϭ3 contributions. The Gamow-Teller ͑GT͒ strength B(GT) in the continuum deduced from the Lϭ0 cross section is compared both with the perturbative calculation by Bertsch and Hamamoto and with the second-order random phase approximation calculation by DroSdS et al. The sum of B(GT) values up to 50 MeV excitation becomes S ␤ Ϫϭ28.0Ϯ1.6 after subtracting the contribution of the isovector spin-monopole strength. This S ␤ Ϫ value of 28.0Ϯ1.6 corresponds to about ͑93 Ϯ 5͒% of the minimum value of the sum rule 3(NϪZ)ϭ30. The usefulness of the polarization transfer observable in the distorted wave impulse approximation is presented. ͓S0556-2813͑97͒02006-2͔

No abstract

Double differential cross sections between 0 • -12 • were measured for the 90 Zr(n, p) reaction at 293 MeV over a wide excitation energy range of 0-70 MeV. A multipole decomposition technique was applied to the present data as well as the previously obtained 90 Zr(p, n) data to extract the Gamow-Teller (GT) component from the continuum. The GT quenching factor Q was derived by using the obtained total GT strengths. The result is Q = 0.88 ± 0.06, not including an overall normalization uncertainty in the GT unit cross section of 16%.The (p, n) reaction at intermediate energies (T p > 100 MeV) provides a highly selective probe of spin-isospin excitations in nuclei due to the energy dependence of the isovector part of nucleon-nucleon (NN ) t-matrices [1]. The

Spin-isospin excitations inBi have been investigated using the Pb( He, t) Bi reaction at and near 6 -0' at R( He)=450 MeV. The microscopic structure of the Gamow-Teller resonance (GTR), the isobaric analog state (IAS), and the spin-Hip dipole (AL = 1) resonance (SDR) in Bi has been studied by observing their direct proton decays to the low-lying neutron-hole states in Pb. Decay protons were measured at backward angles in coincidence with tritons detected at and near O'. The total branching ratio for proton decay from the GTR is determined to be only 4.9+1.370. The total branching ratio for proton decay from the SDR amounts to 14.1+4.2'FD. The deduced total widths as well as the total and partial proton escape widths of the GTR and IAS are found to be in reasonable agreement with recent theoretical estimates obtained in the framework of the continuum Tamm-Dancoff approximation.PACS number(s): 24.30. Cz, 25.55.Kr, 27.80.+w, 29.30.Aj

No abstract