A semimicroscopical approach is applied to calculate: (i) strength functions for the charge-exchange spin-dipole giant resonances in the 208 Pb parent nucleus; (ii) partial and total branching ratios for the direct proton decay of the resonance in 208 Bi. The approach is based on continuum-RPA calculations of corresponding reaction-amplitudes and phenomenological description of the doorway-state coupling to many-quasiparticle configurations. The only adjustable parameter needed for the description is found by comparison of the calculated and experimental total widths of the resonance. Other model parameters used in calculations are taken from independent data. The calculated total branching ratio is found to be in reasonable agreement with the experimental value.

The ( 3 He,t) charge-exchange reaction has been studied at E( 3 He)ϭ450 MeV and angles near 0°on targets of 90 Zr and 208 Pb. Fragmentation of the Gamow-Teller ͑GT͒ strength into separate components of the particlehole type has been observed. The distribution of the GT strength in 90 Nb and in 208 Bi has been calculated within the continuum quasiparticle random phase approximation and continuum-random-phase approximation approaches, respectively. These components, especially in 208 Pb, could be related with the direct, core polarization, and back-spin-flip Gamow-Teller strength.

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The branching ratios for E1 transitions between the spin-dipole ͑SD͒ and Gamow-Teller ͑GT͒ giant resonances in 90 Nb and 208 Pb are evaluated. Assuming the main GT state has a wave function close to that for the ''ideal'' GT state, we reduced the problem to calculate the SD and GT strength functions. These strength functions are evaluated within an extended continuum-random phase approximation approach. PACS number͑s͒: 24.30.Cz, 23.20.Ϫg, 21.60.Jz Experimental and theoretical studies of direct-decay properties of various giant resonances ͑GRs͒ allow one to check their microscopic ͑particle-hole͒ structure in a quantitative way. Experimentally the partial branching ratios for the direct proton decay of both Gamow-Teller GR ͑GTR͒ and the spin-dipole GR (SDR (Ϫ) ) are obtained from the ( 3 He,t) and ( 3 He,tp) experiments. The data at E( 3 He)ϭ450 MeV have been analyzed for the 208 Pb target nucleus ͓1,2͔ and have been rather successfully described within an extended continuum-RPA approach ͓3͔. The data of the 90 Zr( 3 He,tp) reaction are expected to be analyzed soon ͓4͔. Another possibility to reveal the microscopic structure of the SDR (Ϫ) and GTR is to study ␥ transitions between these resonances. The branching ratios for the ␥ decay from the SDR (Ϫ) to the GTR can be deduced from the ( 3 He,t␥) coincidence experiments ͓5͔.The intensity of the E1 ␥ transitions between GT and SD (Ϫ) states in 90 Nb and 48 Sc was evaluated within a TDA approach in Ref. ͓6͔. However, the results obtained in this work are presented in a form which does not allow one to compare them directly with the experimental branching ratios. The aim of the present work is to evaluate the branching ratio for the E1 transitions between the SDR (Ϫ) and the GTR ͑main peak͒ in 208 Bi and 90 Nb within the approach given in Ref. ͓3͔. In this approach we use ͑i͒ the continuum-RPA ͑CRPA͒, ͑ii͒ the phenomenological mean field and the Landau-Migdal particle-hole interaction together with some partial self-consistency conditions, ͑iii͒ a phenomenological description of the doorway-state coupling to manyquasiparticle configurations.We start from consideration of the CRPA polarizabilities P JLS (Ϫ,ϩ) () and the strength functions S JLS (Ϫ,ϩ) () corresponding to the external fields V JLSM (Ϫ,ϩ) ϭ ͚ a V JLSM (Ϫ,ϩ) (x a ). Here, V JLSM (Ϫ,ϩ) (x)ϭr L T JLSM (n ជ ) (Ϫ,ϩ) ͑with JϭSϭ1;Lϭ0 and J ϭ0,1,2;LϭSϭ1 for GT and SD excitations, respectively͒,Ϫm is the irreducible spin-angular tensor operator of the rank J, and ͱ2 (Ϯ) are the spherical spin and isospin Pauli matrices, respectively; is the excitation energy measured from the energy of the parent-nucleus ground state. For the considered spin GRs, the CRPA polarizabilities and the strength functions exhibit resonancelike behavior, corresponding to the excitation of isolated particle-hole type doorway states. In particu-lar, using the Breit-Wigner parametrization of the polarizabilities and the strength functionswe can evaluate the doorway parameters: strength R s(g) , energy s(g) , and total escape width ⌫ s...