β-delayed particle decay of 9C and the A=9, T=1/2 nuclear system:: R-matrix fits, the A=9 nuclear system, and the stellar reaction rate of 4He(αn, γ)9Be -: art. no. 034303

The decay of C-9 (T-1/2 = 126.5 ms) has been observed in two experiments at the TISOL facility at TRIUMF employing different detector configurations for each run. In the first of two papers [E. Gete et al., Phys. Rev. C 61, 064310 (2000)], the experimental technique and data analysis were described. Phenomenological branching ratios and Gamow-Teller strengths were then deduced. In this paper, the data are analyzed using a multichannel, multistate R-matrix approach which leads to a different interpretation of the spectra and therefore modified state energies, widths, branching ratios, and Gamow-Teller strengths, Difficulties in fitting the second excited state of B-9 at 2.34 MeV and possible modifications to the penetrability are described. The existence of a J pi = 1/2(-) state at about 5 MeV excitation energy is suggested from the fits, as well as a considerable decay strength from the B-9 ground state at high energies. Consequences for the properties of the A = 9, T = 1/2 nuclear system are then discussed: in particular, it is shown that the data agree qualitatively with shell model predictions without unusual Gamow-Teller strength present at high excitation energies. Finally, an estimate of the He-4(alphan, gamma)Be-9 stellar reaction rate is given.