Pionic 4f → 3d transition in 181Ta, natural Re, and 209Bi And the strong interaction level shift and width of the pionic 3d state

Abstract

Owing to a powerful Compton-suppression technique it was possible to observe for the first time the pionic 4f → 3d X-ray transition in elements heavier than A = 150. The strong interaction monopole shifts ε 0 and widths Γ 0 as well as the quadrupole splitting of the 3d levels have been measured in Ta, Re and Bi. Thus in addition to the strongly shifted and broadened 5g → 4f transitions, a second, strongly affected line is available for these elements. For the pionic 4f levels, standard optical potentials fit the strong interaction shifts and broadenings quite well. The now observed, deeper-lying 3d states in Ta, Re and Bi have shifts and widths that differ by a factor of 2 or more from the standard optical potential predictions. From the observed relative X-ray intensities of the pionic cascade we also extract the strong interaction widths of the 5g and 4f levels.