Direct proton decay from the Gamow-Teller resonance inBi208

Spin-isospin excitations in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Bi}$ have been investigated using the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ ${(}^3$He,t${)}^{208}$Bi reaction at near θ≊0° at E${(}^3$He)=450 MeV. The microscopic structure of the Gamow-Teller resonance (GTR), the isobaric analog state (IAS), and the spin-flip dipole (ΔL=1) resonance (SDR) in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Bi}$ has been studied by observing their direct proton decays to the low-lying neutron-hole states in ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$. Decay protons were measured at backward angles in coincidence with tritons detected at and near 0°. The total branching ratio for proton decay from the GTR is determined to be only 4.9±1.3%. The total branching ratio for proton decay from the SDR amounts to 14.1±4.2%. The deduced total widths as well as the total and partial proton escape widths of the GRR and IAS are found to be in reasonable agreement with recent theoretical estimates obtained in the framework of the continuum Tamm-Dancoff approximation.