Multistep direct analysis of (p, α) reactions to the continuum

The double differential cross-sections for the (p,α) reaction have been measured for the isotope pairs90,91Zr at 24.02 MeV and142,143Nd at 23.1 MeV. The cross-sections are separated into compound nucleus and multistep direct components by the subtraction method and analyzed using the Hauser-Feshbach and Feshbach-Kerman-Koonin theories. The direct interaction is assumed to take place by the alpha-particle knockout process. The extent to which the unpaired neutrons in91Zr and143Nd act as spectators in the reaction is studied and the role of pairing effects assessed.