Pionic 3d → 2p X-ray measurements in 50,52,54Cr, 45Sc, 51V, 55Mn and Fe

Abstract

We report the measurement of the strong interaction shifts and widths of the pionic 3d → 2p transitions in separated isotopes of 50,52,54Cr and natural Sc, V, Mn, and Fe. Using these new data in combination with earlier low- Z pionic data (6 ⩽ Z ⩽ 20) we have studied the phenomenological pion-nuclear potential. Employing nuclear structure information from measured charge densities and Hartree-Fock calculations, we have fitted the pion-nuclear potential parameters to the pionic-atom data. We have explored the sensitivity of these data to the value of the Lorentz-Lorenz parameter ξ. The addition of an isovector dependence to the s- and p-wave two-nucleon terms is shown to be unnecessary at the present level of experimental accuracy. We have used the deduced optical potentials to determine the neutron radii of the nuclei 20 ⩽ Z ⩽ 26 and find reasonable agreement with Hartree-Fock predictions and with the results of other hadronic probes for 20 ⩽ Z ⩽ 23 but poor agreement for 24 ⩽ Z ⩽ 26.