It has recently been reported [G. W. Bailey et al., Phys. Rev. Lett. 117, 162502 (2016)] that $(d,p)$ cross sections can be very sensitive to the $n\text{−}p$ interactions used in the adiabatic treatment of deuteron breakup with nonlocal nucleon-target optical potentials. To understand to what extent this sensitivity could originate in the inaccuracy of the adiabatic approximation we have developed a leading-order local-equivalent continuum-discretized coupled-channel model that accounts for nonadiabatic effects in the presence of nonlocality of nucleon optical potentials. We have applied our model to the astrophysically relevant reaction ${}^{26m}\mathrm{Al}(d,p){}^{27}\mathrm{Al}$ using two different $n\text{−}p$ potentials associated with the lowest and the highest $n\text{−}p$ kinetic energy in the short-range region of their interaction. Our calculations reveal a significant reduction of the sensitivity to the high $n\text{−}p$ momenta thus confirming that it is mostly associated with theoretical uncertainties of the adiabatic approximation itself. The nonadiabatic effects in the presence of nonlocality were found to be stronger than those in the case of the local optical potentials. These results argue for extending the analysis of the $(d,p)$ reactions, measured for spectroscopic studies, beyond the adiabatic approximation.

We performed $\beta$ and $\gamma$ spectroscopy of ${}^{197g,198g}\mathrm{Os}$ and ${}^{198g}\mathrm{Ir}$, which were produced by multinucleon transfer reactions at the KEK Isotope Separation System (KISS). KISS was designed for the study of nuclear spectroscopy in the vicinity of $N=126$ for astrophysical interests. The $\beta$-decay half-life of ${}^{197g}\mathrm{Os}$ was revised to $91\left(8\right)\mathrm{s}$, while the half-life of ${}^{198g}\mathrm{Os}$ was measured for the first time and found to be $125\left(28\right)\mathrm{s}$. The $\beta$-decay schemes of ${}^{198g}\mathrm{Ir}$ and ${}^{198g}\mathrm{Os}$ were partially established from this spectroscopic study. Based on presently suggested $I^{\pi }={(3/2\text{or}5/2)}^{-}$ and ${\left(0\text{or}1\right)}^{-}$ for ${}^{197g}\mathrm{Os}$ and ${}^{198g}\mathrm{Ir}$, respectively, the first-forbidden transitions of $\nu \left(3p_{3/2}\right)$ or $\nu \left(2f_{5/2}\right)\to \pi \left(2d_{3/2}\right)$ are suggested to be dominant.

We present quantum Monte Carlo calculations of the single- and two-nucleon momentum distributions in selected nuclei for $A\le 16$. We employ local chiral interactions at next-to-next-to-leading order. We find good agreement at low momentum with the single-nucleon momentum distributions derived for phenomenological potentials. The same agreement is found for the integrated two-nucleon momentum distributions at low relative momentum $q$ and low center-of-mass momentum $Q$. We provide results for the two-nucleon momentum distributions as a function of both $q$ and $Q$. The large ratio of $pn$ to $pp$ pairs around $q=2{\mathrm{fm}}^{-1}$ for back-to-back $(Q=0)$ pairs is confirmed up to ${}^{16}\mathrm{O}$, and results are compatible with those extracted from available experimental data.

We present an extension of the identity method initially introduced for particle yield fluctuation studies towards measurements of differential correlations. The extension is developed and illustrated in the context of measurements of the normalized two-particle cumulant $R_2$ but is adaptable to any correlation measurements, including differential flow measurements. The identity method is also extended to account for an arbitrary number of particle identification devices and signals.

Shape coexistence is a ubiquitous phenomenon in the neutron-rich nuclei belonging to (or sitting at the shores of) the $N=20$ island of inversion (IoI). Exact isospin symmetry predicts the same behavior for their mirrors and the existence of a proton-rich IoI around $Z=20$, centered in the (surely unbound) nucleus ${}^{32}\mathrm{Ca}$. In this article we show that in ${}^{36}\mathrm{Ca}$ and ${}^{36}\mathrm{S}$, Coulomb effects break dramatically the mirror symmetry in the excitation energies due to the different structures of the intruder and normal states. The mirror energy difference (MED) of their $2^{+}$ states is known to be very large at $-246$ keV. We reproduce this value and predict the first excited state in ${}^{36}\mathrm{Ca}$ to be a $0^{+}$ at 2.7 MeV, 250 keV below the first $2^{+}$. In its mirror ${}^{36}\mathrm{S}$ the $0^{+}$ lies at 55 keV above the $2^{+}$ measured at 3.291 MeV. Our calculations predict a huge MED of $-720$ keV, that we dub the “colossal” mirror energy difference. A possible reaction mechanism to access the $0_2^{+}$ in ${}^{36}\mathrm{Ca}$ will be discussed. In addition, we theoretically address the MEDs of the $A=34,T=3$ and $A=32,T=4$ mirrors.

Atomic masses of seven $T_z=-1$, $fp$-shell nuclei from ${}^{44}\mathrm{V}$ to ${}^{56}\mathrm{Cu}$ and two low-lying isomers, ${}^{44m}\mathrm{V}$ ($J^{\pi }=6^{+}$) and ${}^{52m}\mathrm{Co}$ ($J^{\pi }=2^{+}$), have been measured with relative precisions of $1\text{–}4\times {10}^{-7}$ with isochronous mass spectrometry (IMS) at the Cooler Storage Ring (CSRe), Lanzhou. The masses of ${}^{56}\mathrm{Cu}$, ${}^{52g,52m}\mathrm{Co}$, and ${}^{44m}\mathrm{V}$ were measured for the first time in this experiment. The mass excesses ($\text{ME"}\mathrm{s}$) of ${}^{44}\mathrm{V}$, ${}^{48}\mathrm{Mn}$, ${}^{50}\mathrm{Fe}$, and ${}^{54}\mathrm{Ni}$ are determined with an order of magnitude improved precision compared to the literature values. ${}^{52g,52m}\mathrm{Co}$ and ${}^{56}\mathrm{Cu}$ are found to be 370 and 400 keV more bound, respectively, while ${}^{44g,44m}\mathrm{V}$ are $\sim 300$ keV less bound than the extrapolations in the Atomic-Mass Evaluation 2012 ($\mathrm{AME}\text{"}12$). The masses of the four $T_z=-1/2$ nuclei ${}^{45}\mathrm{V}$, ${}^{47}\mathrm{Cr}$, ${}^{49}\mathrm{Mn}$, and ${}^{51}\mathrm{Fe}$ are re-determined to be in agreement, within the experimental errors, with the recent JYFLTRAP (University of Jyväskylä, Finland) measurements or with the previous IMS measurements in CSRe. Details of the measurements and data analysis are described, and the impact of the new $\text{ME}$ values on different aspects in nuclear structure are investigated and discussed.

To find candidates for long-lived high-$K$ isomers in even-even $Z=106\text{–}112$ superheavy nuclei, we study dominant $\alpha$-decay channels of two- and four-quasiparticle configurations at a low excitation. Energies are calculated within the microscopic-macroscopic approach with the deformed Woods-Saxon potential. Configurations are fixed by a standard blocking procedure and their energy found by a subsequent minimization over deformations. Different excitation energies of a high-$K$ configuration in parent and daughter nucleus seem particularly important for hindrance of the $\alpha$ decay. A strong hindrance is found for some four-quasiparticle states, particularly $K^{\pi }={20}^{+}$ and/or ${19}^{+}$ states in ${}^{264\text{–}270}\mathrm{Ds}$. Contrary to what was suggested in experimental papers, it is rather a proton configuration that leads to this strong hindrance. If not shortened by the electromagnetic decay, $\alpha$ half-lives of $\sim 1\mathrm{s}$ could open new possibilities for studies of chemical/atomic properties of related elements.

Background: Projectile fragmentation is a well-established technique to produce rare isotope beams, but its underlying physical processes are not fully known.

Purpose: We devote ourselves to studying the dynamical properties and secondary decay effects of projectile fragmentations in ${}^{124}\mathrm{Sn}, {}^{107}\mathrm{Sn}+{}^{120}\mathrm{Sn}$ collisions at 600 MeV/nucleon.

Method: The formation of the projectile spectator and the fragmentation process are studied with the isospin-dependent quantum molecular dynamics (IQMD) model. The minimum spanning tree algorithm and the ratio of parallel to transverse quantities are applied to distinguish the equilibrated projectile spectator during the dynamics evolution. The influence of secondary decay on fragmentation observables is investigated by comparing the calculations with and without the statistical code gemini. The validity of the theoretical approach is tested by comparing the calculated product yields with the experimental results of the ALADIN Collaboration for the studied reactions.

Results: The general correlation of an increasing excitation energy with a decreasing mass of the spectator system is found for collisions with impact parameter of $b=5$–10 fm. The nucleon evaporation of the prefragments reduces the multiplicity of intermediate-mass fragments, but does not change their dependence on the isospin of the projectile. The sequential decay also leads to narrower isotope distributions. Switching to gemini at a higher excitation energy results in slightly narrower isotope distributions. With the gemini code, in which the nuclear masses with shell and pairing corrections are adopted, the calculations can rather generally reproduce the data of the isotope distributions and mean neutron-to-proton ratios of the light fragments.

Conclusion: By permitting only evaporation in gemini, the IQMD+gemini model is able to reproduce the main features of projectile fragmentation in the studied Sn+Sn reactions.

We examine the autocorrelation function of the ${}^{235}\mathrm{U}(n,f)$ reaction with a view to quantify the presence of intermediate structure in the cross section. Fluctuations due to compound nucleus resonances on the eV energy scale are clearly visible up to $\approx 100$ keV neutron energies. Structure on the one-keV energy scale is not present as a systematic feature of the correlation function, although it is present in the data covering the region around 20 keV.

Based on a baryon-baryon interaction model with meson exchanges, we investigate the origin of the strong attraction in the $N\mathrm{\Omega }\left({}^{5}S_2\right)$ interaction, which was indicated by recent lattice QCD simulations. The long-range part of the potential is constructed by the conventional mechanisms, the exchanges of the $\eta$ meson and of the correlated two mesons in the scalar-isoscalar channel, denoted by “$\sigma$” in the literature. The short-range part is represented by the contact interaction. We find that the meson exchanges do not provide sufficient attraction. This means that most of the attraction is attributed to the short-range contact interaction. We then evaluate the effect of the coupled channels to the $N\mathrm{\Omega }\left({}^{5}S_2\right)$ interaction. We find that, while the $D$-wave mixing of the $N\mathrm{\Omega }$ channel is negligible, the inelastic $\mathrm{\Lambda }\mathrm{\Xi }$, $\mathrm{\Sigma }\mathrm{\Xi }$, and $\mathrm{\Lambda }\mathrm{\Xi }\left(1530\right)$ channels via the $K$ meson exchange give the attraction of the $N\mathrm{\Omega }\left({}^{5}S_2\right)$ interaction to the same level with the elastic meson exchanges. Although the elimination of these channels induces the energy dependence of the single-channel $N\mathrm{\Omega }$ interaction, this effect is not significant. With the present model parameters fit to reproduce the scattering length of the HAL QCD result of the nearly physical quark masses, we obtain the $N\mathrm{\Omega }\left({}^{5}S_2\right)$ quasibound state with its eigenenergy $2611.3-0.7i\text{MeV}$, which corresponds to the binding energy $0.1\text{MeV}$ and width $1.5\text{MeV}$ for the decay to the $\mathrm{\Lambda }\mathrm{\Xi }$ and $\mathrm{\Sigma }\mathrm{\Xi }$ channels. From the analysis of the spatial structure and the compositeness, the quasibound state is shown to be the molecular state of $N\mathrm{\Omega }$. We also construct an equivalent local potential for the $N\mathrm{\Omega }\left({}^{5}S_2\right)$ system which is useful for various applications.

Matter radii of the ${}^{34–40}\mathrm{Mg}$ nuclei are investigated by self-consistent Hartree-Fock-Bogolyubov calculations assuming the axial symmetry. With the semirealistic M3Y-P6 interaction, the $N$ dependence of the matter radii observed in the experiments is reproduced excellently. Both the pairing and the deformation play significant roles in an intertwined manner. The ${}^{35}\mathrm{Mg}$ nucleus has a smaller radius than the neighboring even-$N$ nuclei, which is attributed to its smaller deformation. On the other hand, a neutron halo is obtained in ${}^{37}\mathrm{Mg}$. We point out that, in contrast to the pairing antihalo effect that may operate on the even-$N$ nuclei, the pair correlation enhances halos in odd-$N$ nuclei, owing to the new mechanism which we call unpaired-particle haloing. The halo in ${}^{37}\mathrm{Mg}$ is predicted to have a peanut shape in its intrinsic state, reflecting $p$-wave contribution as in ${}^{40}\mathrm{Mg}$. The $N$ dependence of the deformation is significant again, by which the single-particle level dominated by the $p$-wave component comes down.

Multistrange Ca, Sn, and Pb hypernuclei with $\mathrm{\Lambda }\mathrm{\Lambda }$ pairing interaction are investigated within the Hartree-Fock-Bogoliubov approach. The unknown $\mathrm{\Lambda }\mathrm{\Lambda }$ pairing strength is calibrated to match with the maximal value for the prediction of the $\mathrm{\Lambda }$ pairing gap in uniform matter for densities and isospin asymmetries equivalent to those existing in multi-$\mathrm{\Lambda }$ hypernuclei. In this way, we provide an upper bound for the prediction of the $\mathrm{\Lambda }$ pairing gap and its effects in hypernuclei. The condensation energy is predicted to be about 3 MeV as a maximum value, yielding small corrections on density distributions and shell structure. In addition, conditions on both Fermi energies and orbital angular momenta are expected to quench the nucleon-$\mathrm{\Lambda }$ pairing for most of hypernuclei.

Background: Reactions involving weakly bound projectiles with $\alpha +x$ cluster structure are known to produce a large number of $\alpha$ particles, where transfer-induced breakup is one of the possible origins. Detailed investigation on each of these channels is desirable to understand the underlying reaction mechanism.

Purpose: Our purpose is to measure the $+1p$ transfer-induced breakup in the ${}^{112}\mathrm{Sn}({}^7\mathrm{Li},{}^8\mathrm{Be}\to 2\alpha )$ reaction to understand the possible modes of ${}^8\mathrm{Be}$ breakup and their contribution to inclusive $\alpha$ production.

Methods: $\alpha -\alpha$ coincidence measurements have been carried out for the above reaction at $E_{\mathrm{beam}}=30$ MeV. Projectile-like fragments were detected using five sets of Si-strip-detector telescopes and five sets of single Si-detector telescopes. Optical model analysis of elastic scattering data, coupled reaction channels (CRC), and continuum discretized coupled channels (CDCC) calculations were performed to understand the measured cross sections.

Results: The experimental cross sections for $+1p$ transfer-induced breakup in (${}^7\mathrm{Li},{}^8\mathrm{Be}\to 2\alpha$) reaction through different resonance states of ${}^8\mathrm{Be}$ have been obtained. Relative energy distribution and Monte Carlo simulation confirm the observation of breakup of ${}^8\mathrm{Be}$ from its $4^{+}$ (11.35-MeV) resonant state for the first time along with its well-known $0^{+}$ (92-keV) and $2^{+}$ (3.12-MeV) resonances. Simultaneous description of elastic scattering, transfer, and breakup cross sections have been made using CDCC plus CRC formalism.

Conclusions: Production of $\alpha$ particles in $+1p$ transfer-triggered breakup is found to proceed mainly through three resonance ($0^{+},2^{+}$, and $4^{+}$) states of ${}^8\mathrm{Be}$.

We present the first attempt to extract the scalar dipole dynamical polarizabilities from proton real Compton scattering data below pion-production threshold. The theoretical framework combines dispersion relations technique, low-energy expansion, and multipole decomposition of the scattering amplitudes. The results are obtained with statistical tools that have never been applied so far to Compton scattering data and are crucial to overcome problems inherent to the analysis of the available data set.

To develop methods for open quantum systems is one of the most important tasks in theoretical studies. We develop the resonant-continuum relativistic mean-field theory in complex momentum representation with the BCS approximation for pairing correlations in weakly bound nuclei. The bound states and resonant states are treated on the same footing and the physical resonant states are considered self-consistently in the present calculations. The Zr isotopes are chosen as illustrative examples. The calculated binding energies, two-neutron separation energies, and root-mean-square radii are in excellent agreement with the available data as well as the relativistic Hartree-Bogoliubov calculations. Especially, several resonant states lying near the continuum threshold are found to play important roles in the formation of exotic phenomena and support the prediction of giant halo in the Zr isotopes.

The first excited isomeric state of Th-229 has an exceptionally low energy of only a few eV and could form the gateway to high-precision laser spectroscopy of nuclei. The excitation energy of the isomeric state has been inferred from precision $\gamma$ spectroscopy, but its uncertainty is still too large to commence laser spectroscopy. Reducing this uncertainty is one of the most pressing challenges in the field. Here we present an approach to infer the energy of the isomer from spectroscopy of the electron which is emitted when the isomer de-excites through internal conversion (IC). The experiment builds on U-233, which $\alpha$-decays to Th-229 and populates the isomeric state with a 2% branching ratio. A film of U-233 is covered by a stopping layer of few-nm thickness and placed between an $\alpha$ detector and an electron detector, such that the $\alpha$ particle and the IC electron can be detected in coincidence. Retarding field electrodes allow for an energy measurement. In the present design, the signal of the Th-229m IC electrons is masked by low-energy electrons emitted from the surface of the metallic stopping layer. We perform reference measurements with U-232 and U-234 to study systematic effects, and we study various means to reduce the background of low-energy electrons. Our study gives guidelines to the design of an experiment that is capable of detecting the IC electrons and measuring the isomer energy.

The fusion-by-diffusion model proposed by Swiatecki et al. [Phys. Rev. C 71, 014602 (2005)] has provided a simple and convenient tool to estimate evaporation residue cross sections for superheavy nuclei. I extend this model by taking into account deformation of the target nucleus, and discuss the role of orientation of a deformed target in hot fusion reactions at energies around the Coulomb barrier. To this end, I introduce an injection point for the diffusion process over an inner barrier which depends on the orientation angle. I apply this model to the ${}^{48}\mathrm{Ca}+{}^{248}\mathrm{Cm}$ reaction and show that the maximum of evaporation residue cross section appears at an energy slightly above the height of the capture barrier for the side collision, for which the effective inner barrier is considerably lower than that for the tip collision, thus enhancing the diffusion probability. I also discuss the energy dependence of the injection point, and show that a large part of the energy dependence found in the previous analyses can be attributed to the deformation effect of a target nucleus.

Background: High-accuracy data are needed to advance microscopic descriptions of the nuclear fission process, to improve the predictive precision of phenomenological models, and for applications in nuclear energy and homeland security.

Purpose: The main goal of this work is to provide high-accuracy cross-section data for photofission of ${}^{235}\mathrm{U}$, ${}^{238}\mathrm{U}$, and ${}^{239}\mathrm{Pu}$ in the energy range from the fission threshold to the high-energy tail of the giant dipole resonance. These new data should contribute significantly to the reduction of the systematic uncertainty in evaluated photofission cross-section databases.

Method: Cross-section ratios for photofission of the “big three” actinide nuclei were measured using a quasimonoenergetic photon beam and dual-fission chambers. The measurements were performed at the $\mathrm{HI}\gamma \mathrm{S}$ facility using a photon beam produced from Compton backscattering of free-electron laser light. The dual-fission chamber enabled simultaneous counting of fission events from two targets. This method allows for cross-section ratio measurements with very small systematic errors. The largest source of systematic error in the determination of the cross-section ratios is the uncertainty in the ratio of the target thicknesses.

Results: We report photon-induced fission cross-section ratios for $\sigma [{}^{235}\mathrm{U}(\gamma ,f)/{}^{238}\mathrm{U}(\gamma ,f)]$, $\sigma [{}^{235}\mathrm{U}(\gamma ,f)/{}^{239}\mathrm{Pu}(\gamma ,f)]$, and $\sigma [{}^{238}\mathrm{U}(\gamma ,f)/{}^{239}\mathrm{Pu}(\gamma ,f)]$ at photon energies from 9.0–17.0 MeV. More than 20 data points were measured for each ratio, and the systematic uncertainties are less than $2\%$.

Conclusion: The present photofission cross-section ratio data sets are compared to ratios computed from previous measurements, to the corresponding neutron-induced fission cross-section ratios, and to ratios computed from evaluated databases. The data obtained in this work for $\sigma [{}^{235}\mathrm{U}(\gamma ,f)/{}^{238}\mathrm{U}(\gamma ,f)]$ are consistent with the existing data, while for $\sigma [{}^{235}\mathrm{U}(\gamma ,f)/{}^{239}\mathrm{Pu}(\gamma ,f)]$ and $\sigma [{}^{238}\mathrm{U}(\gamma ,f)/{}^{239}\mathrm{Pu}(\gamma ,f)]$ the present data are systematically lower.

Isochronous mass spectrometry has been applied in the storage ring CSRe to measure the masses of the $T_z=-3/2$ nuclei ${}^{27}\mathrm{P}$ and ${}^{29}\mathrm{S}$. The new mass excess value $\text{ME}\left({}^{29}\mathrm{S}\right)=-3094\left(13\right)\mathrm{keV}$ is 66(52) keV larger than the result of the previous ${}^{32}\mathrm{S}({}^3\mathrm{He},{}^6\mathrm{He}){}^{29}\mathrm{S}$ reaction measurement in 1973 and a factor of 3.8 more precise. The new result for ${}^{29}\mathrm{S}$ together with those of the $T=3/2$ isobaric analog states in ${}^{29}\mathrm{P}, {}^{29}\mathrm{Si}$, and ${}^{29}\mathrm{Al}$ fit well into the quadratic form of the isobaric multiplet mass equation (IMME). The mass excess of ${}^{27}\mathrm{P}$ has been remeasured to be $\text{ME}\left({}^{27}\mathrm{P}\right)=-685\left(42\right)\mathrm{keV}$. By analyzing the linear and quadratic coefficients of the IMME in the $T_z=-3/2 sd$-shell nuclei, it was found that the ratio of the Coulomb radius parameters is $R\approx 0.96$ and is nearly the same for all $T=3/2$ isospin multiplets. Such a nearly constant $R$ value, apparently valid for the entire light mass region with $A>9$, can be used to set stringent constraints on the isovector and isotensor components of the isospin nonconserving forces in theoretical calculations.