Systematics of continuum pion double charge exchange on T = 0 nuclei

Pion double-charge-exchange cross sections have been measured at forward angles for targets of /sup 12/C, /sup 24/Mg, /sup 28/Si, /sup 32/S, and /sup 40/Ca at incident pion energies of 120--210 MeV. Angular distributions were obtained at 164 MeV for the lightest ( /sup 12/C) and heaviest ( /sup 40/Ca) targets. Pions corresponding to excitation energies up to 25 MeV in the final nuclei have been detected. Double differential cross sections d/sup 2/sigma/d..cap omega.. dE are presented and the dependence on target mass, incident pion energy, excitation energy, and scattering angle has been investigated. The summed cross sections show a much smoother energy dependence than the ground state transition and mass dependence as A/sup p/, with p varying with excitation energy rougly from -2 to -1. The excitation functions for the discrete nonanalog transitions to the first 2/sup +/ state in /sup 12/O and /sup 40/Ti have been measured.