Concentrated particle-hole strength observed in 0hω stretched-state excitations

The wide-angle spectra of the 134-MeV (p,n) reaction on 48Ca, 54Fe, 88Sr, and 208Pb are each dominated by the excitation of a single state at low excitation energy. These excitations correspond to the ''0hω'' stretched states and are seen to be fragmented much less than ''1hω'' stretched states in medium- and heavy-mass nuclei. The normalization factors required for comparison with distorted-wave impulse-approximation calculations are >0.50 and indicate that these are the purest particle-hole states known in these nuclei