3D-]2P PIONIC TRANSITION IN NI58 AND NI60

The 3d2p pionic x rays in Ni58 and Ni60 have been observed in order to measure effects due to the strong interaction between the pion and the nucleus. These isotopes were chosen because nuclear effects in the x-ray energy are expected to be large and the x-ray yield is appreciable. We see a large nuclear level shift and broadening, but no isotope effect within experimental error. The level shift is found to have a strong dependence on the neutron radius, and our results are consistent with the hypothesis of equal neutron and proton rms radii. We also compute the isotope shift for the 2p1s transition in O16 and O18 and find that experimental measurements require the neutron radius of O18 to be greater than the neutron radius of O16. However, uncertainties in the pion-nuclear interaction do not allow an accurate determination of the neutron radius. © 1969 The American Physical Society.