Particle-hole strength excited in the ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$(p,n${)}^{48}$Sc reaction at 134 and 160 MeV: (π$f_{7/2}$,ν$f_{7/2}^{\mathrm{-}1}$) band

The ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$(p,n${)}^{48}$Sc reaction was studied at 134 and 160 MeV. Neutron energy spectra were measured by the time-of-flight technique with resolutions from 320 to 460 keV at 11 angles from 0° to 60° spaced approximately 6° apart. The neutron spectra reveal strong excitation of the (π$f_{7/2}$,ν$f_{7/2}^{\mathrm{-}1}$) band of states at low excitation energies; five of the known eight members of the band are excited strongly, generally consistent with distorted-wave-impulse-approximation calculations with 1f-2p shell-model wave functions. The normalization of the distorted-wave-impulse-approximation calculations to the extracted angular distributions at 135 MeV vary from 0.40 for the $5^{+}$ state to 0.93 for the $0^{+}$, isobaric analog state. The normalization factor of 0.60 required for the $7^{+}$, stretched-state transition is significantly larger than those required for similar distorted-wave-impulse-approximation calculations of various stretched-state excitations observed in inelastic proton scattering, which involve promoting a nucleon up into the next major shell (a ‘‘1 ħω’’ excitation). The larger normalization factor required for the (π$f_{7/2}$,ν$f_{7/2}^{\mathrm{-}1}$) $7^{+}$ excitation (a ‘‘0 ħω’’ excitation) indicates that this strength is more highly concentrated in a single state. The $4^{+}$ and $6^{+}$ states of this band are observed to be only weakly excited, consistent with predictions that transitions dominated by the tensor term of the nucleon-nucleon interaction will predominantly excite non-normal parity states. The excitation of the $2^{+}$ member of this band shows both Δl=0 and Δl=2 contributions to the angular distribution and may indicate significant two-step processes for this transition.