Resonance structure of [Formula Presented] and [Formula Presented] in a microscopic cluster model

Resonance structures of excited states in [Formula Presented] and [Formula Presented] are studied by means of a microscopic multicluster model. The two-body scattering of [Formula Presented] or [Formula Presented] is solved by the microscopic R-matrix method where two-cluster wave functions of [Formula Presented] and [Formula Presented] are employed. These results are compared with the [Formula Presented] three-body complex scaling method to check the validity of neglecting three-body channels in the microscopic R-matrix method. The [Formula Presented] first excited state of [Formula Presented] which cannot be identified in the complex scaling method, is given as a [Formula Presented] virtual state with a purely imaginary complex momentum, and this resonance lies on the second Riemann sheet only for the [Formula Presented] channel. The [Formula Presented] resonance of the mirror nucleus [Formula Presented] has a very large width, and its excitation energy as obtained from the analytic continuation of the S matrix to the complex energies shows a normal Thomas-Ehrman shift. The dimensionless reduced widths and the reduced width amplitudes are calculated for low-lying resonances, and the cluster structure of these states in [Formula Presented] is discussed. © 2003 The American Physical Society.SCOPUS: ar.j