Excitation of two nucleons into the continuum as a doorway process for bound-pion absorption by nuclei

The problem of bound-pion absorption by nuclei has been studied in a semimicroscopic way. Calculations of the widths of the 1s, 2p and 3d levels in ¹²C, ¹⁴N, ^16-18O, ¹⁹F, ²⁰Ne, ²³Na, ^24-26Mg, ²⁷Al, ²⁸Si, ³¹P, ³²S, ³⁵Cl, ³⁹K, ⁴⁰Ar, ^40-48Ca, ^46-50Ti, ⁵¹V and ⁵²Cr and the 4f level in ²⁰⁹Bi pi ^--atoms based on the nuclear self-consistent theory of Birbrair et al. (1978) and Alkhazov et al. (1978) are performed assuming that the 'two-nucleon' mechanism is the doorway process for nuclear pion absorption (Birbrair and Kalashnikov). Both P and S absorption mechanisms together with their interference are included here. This enables us to calculate the widths of the 1s levels where S absorption dominates. The results are in good agreement with experiment.