Nuclear structure of the spin-isospin excited states in ¹³N studied via the (³He,t) and (³He,tp) reactions at 450 MeV

Spin-isospin excitations in ¹³N have been studied by means of the (³He,t) and (³He,tp) reactions at a bombarding energy of E(³He)=450 MeV. The zero-degree (³He,t) spectrum is found to be similar to those from the (p,n) reactions at intermediate energies, suggesting a simple direct reaction mechanism at E(³He) =450 MeV. The Gamow-Teller (GT) states with J^π=1/2^- and 3/2 ^- have been strongly excited at θ_lab=0°. The angular distribution of cross sections for the ¹³C( ³He,t)¹³N reaction and the elastic ³He scattering off ¹³C were obtained at θ_lab=0° - 17° and at θ_lab=2° - 22°, respectively. The obtained experimental results were compared with calculations performed in distorted-wave Born approximation. Microscopic structures of the states in ¹³N have further been studied by observing decay protons in coincidence with high-energy tritons measured at θ_lab=0°. The branching ratios for proton decay from the GT states in ¹³N to the final low-lying T=0 states in ¹²C were obtained. The wave functions of the excited states in ¹³N are discussed on the basis of obtained experimental data and relevant theoretical calculations.