Analog States ofSr89and the Particle-Core Model in theN=50Region

Analog resonances in ($p, p$) and ($p, p^{\prime }$) excitation functions on ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}$ have been studied, and previous data have been extended to complete the range from $E_p=4.8\mathrm{} \mathrm{to} 12$ MeV and include residual channels up to $E_x=4.5\mathrm{}$ MeV in the target system. The various reaction mechanisms contributing to the observed structure are assayed. A comparison of the present data with similar experimental results in this mass region has been made, and the empirical evidence for particle-core coupling in the spectra of several odd-$A$ nuclei near $N=50\mathrm{}$ has been stressed. The possible existence of composite particle-core structure involving the $0_1^{+}$ and collective $2_1^{+}$ and $3_1^{-}$ cores is discussed and a consequent means of populating two-phonon $2_1^{+}$×$3_1^{-}$ state is suggested. Evidence for particle coupling to noncollective core excitations is also cited.