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.

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.

Excited states in ${}^{38,40,42}\mathrm{Si}$ nuclei have been studied via in-beam $\gamma$-ray spectroscopy with multinucleon removal reactions. Intense radioactive beams of ${}^{40}\mathrm{S}$ and ${}^{44}\mathrm{S}$ provided at the new facility of the RIKEN Radioactive Isotope Beam Factory enabled $\gamma \mathrm{\text{−}}\gamma$ coincidence measurements. A prominent $\gamma$ line observed with an energy of 742(8) keV in ${}^{42}\mathrm{Si}$ confirms the $2^{+}$ state reported in an earlier study. Among the $\gamma$ lines observed in coincidence with the $2^{+}\to 0^{+}$ transition, the most probable candidate for the transition from the yrast $4^{+}$ state was identified, leading to a $4_1^{+}$ energy of 2173(14) keV. The energy ratio of 2.93(5) between the $2_1^{+}$ and $4_1^{+}$ states indicates well-developed deformation in ${}^{42}\mathrm{Si}$ at $N=28$ and $Z=14$. Also for ${}^{38,40}\mathrm{Si}$ energy ratios with values of 2.09(5) and 2.56(5) were obtained. Together with the ratio for ${}^{42}\mathrm{Si}$, the results show a rapid deformation development of Si isotopes from $N=24$ to $N=28$.

Intermediate-energy Coulomb excitation measurements are performed on the $N\ge 40$ neutron-rich nuclei ${}^{66,68}\mathrm{Fe}$ and ${}^{64}\mathrm{Cr}$. The reduced transition matrix elements providing a direct measure of the quadrupole collectivity $B(E2;2_1^{+}\to 0_1^{+})$ are determined for the first time in ${}^{68}\mathrm{Fe}_{42}$ and ${}^{64}\mathrm{Cr}_{40}$ and confirm a previous recoil distance method lifetime measurement in ${}^{66}\mathrm{Fe}_{40}$. The results are compared to state-of-the-art large-scale shell-model calculations within the full $fpgd$ neutron orbital model space using the Lenzi-Nowacki-Poves-Sieja effective interaction and confirm the results of the calculations that show these nuclei are well deformed.

An approach is presented to experimentally constrain previously unreachable ($p$, $\gamma$) reaction rates on nuclei far from stability in the astrophysical $rp$ process. Energies of all critical resonances in the ${}^{57}\mathrm{Cu}(p,\gamma ){}^{58}\mathrm{Zn}$ reaction are deduced by populating states in ${}^{58}\mathrm{Zn}$ with a ($d$, $n$) reaction in inverse kinematics at $75\mathrm{MeV}/u$, and detecting $\gamma$-ray-recoil coincidences with the state-of-the-art $\gamma$-ray tracking array GRETINA and the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The results reduce the uncertainty in the ${}^{57}\mathrm{Cu}(p,\gamma )$ reaction rate by several orders of magnitude. The effective lifetime of ${}^{56}\mathrm{Ni}$, an important waiting point in the $rp$ process in x-ray bursts, can now be determined entirely from experimentally constrained reaction rates.

Excited states in ${}^{16}$C were populated via the ${}^9$Be(${}^{17}$N,${}^{16}$C+$\gamma$)X one-proton knockout reaction. The lifetime of the 2${}_1^{+}$ state in ${}^{16}$C was measured using the recoil distance method. The extracted lifetime of ${\tau }_{2_1^{+}}=11.4_{-0.9}^{+0.8}\left(\text{stat}\right)\pm 0.7{\left({\text{syst}}_{B\rho }\right)}_{-1.5}^{+0.0}\left({\text{syst}}_{\text{feeding}}\right)$ ps yields a deduced $B(E2;2_1^{+}\to 0_1^{+})=4.{21}_{-0.26}^{+0.34}{\left(\text{stat}\right)}_{-0.24}^{+0.28}{\left({\text{syst}}_{B\rho }\right)}_{-0.00}^{+0.64}\left({\text{syst}}_{\text{feeding}}\right)e^2{\mathrm{fm}}^4$ value in good agreement with a previous measurement. The one-proton knockout cross section is used to extract the proton amplitude of the ${}^{16}$C 2${}_1^{+}$ state, which confirms the neutron dominant character of this state. Gamma-ray branching ratios between the 2${}_2^{+}$ state and the 2${}_1^{+}$ and ground states were also determined. The results are compared with $p-sd$ shell model and no-core shell model (with $NN$ and $NN+NNN$) calculations. The inclusion of three-body forces are essential in order for the no-core shell model calculations to reproduce the experimental findings on the $\gamma$-ray branching ratios.