Both one-proton and one-neutron knockout reactions were performed with fast beams of two asymmetric, neutron-deficient rare isotopes produced by projectile fragmentation. The reactions are used to probe the nucleon spectroscopic strengths at both the weakly and strongly bound nucleon Fermi surfaces. The one-proton knockout reactions ${}^9\mathrm{Be}$(${}^{28}\mathrm{S}$,${}^{27}\mathrm{P}$)X and ${}^9\mathrm{Be}$(${}^{24}\mathrm{Si}$,${}^{23}\mathrm{Al}$)X probe the weakly bound valence proton states and the one-neutron knockout reactions and ${}^9\mathrm{Be}$(${}^{28}\mathrm{S}$, ${}^{27}\mathrm{S}$)X and ${}^9\mathrm{Be}$(${}^{24}\mathrm{Si}$, ${}^{23}\mathrm{Si}$)X the strongly bound neutron states in the two systems. The spectroscopic strengths are extracted from the measured cross sections by comparisons with an eikonal reaction theory. The reduction of the experimentally deduced spectroscopic strengths, relative to the predictions of shell-model calculations, is of order 0.8–0.9 in the removal of weakly bound protons and 0.3–0.4 in the knockout of the strongly bound neutrons. These results support previous studies at the extremes of nuclear binding and provide further evidence that in asymmetric nuclear systems the nucleons of the deficient species, at the more-bound Fermi surface are more strongly correlated than those of the more weakly bound excess species.

The neutron-rich nucleus ${}^{144}\mathrm{Ba}$ ($t_{1/2}=11.5\mathrm{s}$) is expected to exhibit some of the strongest octupole correlations among nuclei with mass numbers $A$ less than 200. Until now, indirect evidence for such strong correlations has been inferred from observations such as enhanced $E1$ transitions and interleaving positive- and negative-parity levels in the ground-state band. In this experiment, the octupole strength was measured directly by sub-barrier, multistep Coulomb excitation of a post-accelerated 650-MeV ${}^{144}\mathrm{Ba}$ beam on a $1.0\text{−}\mathrm{mg}/{\mathrm{cm}}^2$ ${}^{208}\mathrm{Pb}$ target. The measured value of the matrix element, $⟨{3_1}^{-}\parallel \mathcal{M}(E3)\parallel {0_1}^{+}⟩=0.65\left(\genfrac{}{}{0ex}{}{+17}{-23}\right)$ $e{b}^{3/2}$, corresponds to a reduced $B(E3)$ transition probability of $48\left(\genfrac{}{}{0ex}{}{+25}{-34}\right)\mathrm{W}.\mathrm{u}.$ This result represents an unambiguous determination of the octupole collectivity, is larger than any available theoretical prediction, and is consistent with octupole deformation.

The even ${}^{52-56}\mathrm{Ti}$ isotopes have been studied with intermediate-energy Coulomb excitation and absolute $B(E2;0^{+}\to 2_1^{+})$ transition rates have been obtained. These data confirm the presence of a subshell closure at neutron number $N=32$ in neutron-rich nuclei above the doubly magic nucleus ${}^{48}\mathrm{Ca}$ and provide no direct evidence for the predicted $N=34$ closure. Large-scale shell model calculations with the most recent effective interactions are unable to reproduce the magnitude of the measured strengths in the semimagic Ti nuclei and their strong variation with neutron number.

Despite the more than 1 order of magnitude difference between the measured dipole moments in ${}^{144}\mathrm{Ba}$ and ${}^{146}\mathrm{Ba}$, the octupole correlations in ${}^{146}\mathrm{Ba}$ are found to be as strong as those in ${}^{144}\mathrm{Ba}$ with a similarly large value of $B(E3;3^{-}\to 0^{+})$ determined as $48(\begin{array}{c}+21\\ -29\end{array})\mathrm{W}.\mathrm{u}.$ The new results not only establish unambiguously the presence of a region of octupole deformation centered on these neutron-rich Ba isotopes, but also manifest the dependence of the electric dipole moments on the occupancy of different neutron orbitals in nuclei with enhanced octupole strength, as revealed by fully microscopic calculations.

The two-proton knockout reaction ${}^9\mathrm{Be}$(${}^{54}\mathrm{Ti}$,${}^{52}\mathrm{Ca}+\gamma$) has been studied at 72 MeV/nucleon. Besides the strong feeding of the ${}^{52}\mathrm{Ca}$ ground state, the only other sizeable cross section proceeds to a $3^{-}$ level at 3.9 MeV. There is no measurable direct yield to the first excited $2^{+}$ state at 2.6 MeV. The results illustrate the potential of such direct reactions for exploring cross-shell proton excitations in neutron-rich nuclei and confirms the doubly-magic nature of ${}^{52}\mathrm{Ca}$.