In this article we report on the first spectroscopic information on ${}_{51}{}^{140}\mathrm{Sb}_{89}$ and the observation of an isomer in this nucleus with $T_{1/2}=41\left(8\right)$ $\mu \mathrm{s}$. It is located in close proximity to ${}^{140}\mathrm{Sn}$ for $N=90$, where the $\nu f_{7/2}$ orbit is completely filled. The possible origin of the isomeric state is a $\pi g_{7/2}^1\times \nu f_{7/2}^{-1}$ coupling configuration, resulting in a $\left(6^{-}\right)$ or $\left(7^{-}\right)$ spin-parity. This is likely caused by an inversion of the $\pi g_{7/2}$ and $\pi d_{5/2}$ orbitals at $N=89$. The existence of such an isomer far from stability is discussed extensively in the context of shell-model calculations and compared to results from mean-field calculations performed using a deformed Woods-Saxon potential. Both approaches suggest the observation of a single-particle excitation mode at an extreme neutron number.

The configuration-interaction shell model with the WBP10 effective interaction has been used to investigate the pygmy and giant dipole resonances in the nitrogen isotopes. Large enhancement of low-lying dipole strength, i.e., pygmy dipole resonances (PDRs), is predicted in the neutron-rich ${}^{17,18,19,20}\mathrm{N}$. The nature of the PDRs is analyzed via the transition densities and transition matrix elements. It turns out these PDRs involve a larger amount of excitations between the $2s1d$ and loosely bound $1f2p$ shells. Combining with the transition densities, it is concluded that the PDRs in ${}^{17,18,19,20}\mathrm{N}$ are collective and due to the oscillation between the excess neutrons and the isospin saturated core. The isospin dependence of energy splitting and sum rule of isospin doublets is discussed. The theoretical energy splitting of isospin doublets can significantly deviate from the systematic values when nucleus is far away from the $\beta$-stability line. The ratios of $T_{<}$ and $T_{>}$ energy-weighted sum rule (EWSR) are consistently larger than the systematic values, and it is noticed that the calculated EWSR ratio over the systematic ratio increases with increasing isospin almost linearly. We also calculated the photoabsorption cross sections for the nitrogen isotopes. We proposed the normalization factors for $0–1\hslash \omega$ and $2–3\hslash \omega$ calculations. After the normalization, the shell model has well reproduced the experimental photoabsorption cross sections in ${}^{14,15}\mathrm{N}$, especially the detailed structure of resonances.

The low-lying $M1$ strength of the open-shell nucleus ${}^{50}\mathrm{Cr}$ has been studied with the method of nuclear resonance fluorescence up to 9.7 MeV using bremsstrahlung at the superconducting Darmstadt linear electron accelerator S-DALINAC and Compton backscattered photons at the High Intensity $\gamma$-ray Source $\left(\mathrm{HI}\gamma \mathrm{S}\right)$ facility between 6 and 9.7 MeV of the initial photon energy. Fifteen $1^{+}$ states have been observed between 3.6 and 9.7 MeV. Following our analysis the lowest $1^{+}$ state at 3.6 MeV can be considered as an isovector orbital mode with some spin admixture. The obtained results generally match the estimations and trends typical for the scissors-like mode. Detailed calculations within the Skyrme quasiparticle random-phase-approximation method and the large-scale shell model justify our conclusions. The calculated distributions of the orbital current for the lowest $1^{+}$-state suggest the schematic view of Lipparini and Stringari (isovector rotation-like oscillations inside the rigid surface) rather than the scissors-like picture of Lo Iudice and Palumbo. The spin $M1$ resonance is shown to be mainly generated by spin-flip transitions between the orbitals of the $fp$ shell.

We examine the momentum dependence of $\overline{p}p$ and $\overline{n}p$ annihilation cross sections by considering the transmission through a nuclear potential and the $\overline{p}p$ Coulomb interaction. Compared to the $\overline{n}p$ annihilation cross section, the $\overline{p}p$ annihilation cross section is significantly enhanced by the Coulomb interaction for projectile momenta below $p_{\mathrm{lab}}<500$ MeV/$c$, and the two annihilation cross sections approach the Pomeranchuk's equality limit [JETP Lett. 30, 423 (1956)] at $p_{\mathrm{lab}}\sim 500$ MeV/$c$. Using these elementary cross sections as the basic input data, the extended Glauber model is employed to evaluate the annihilation cross sections for $\overline{n}$ and $\overline{p}$ interaction with nuclei and the results compare well with experimental data.

We analyze the nucleon structure of the $\alpha$-decaying nucleus to see if it can be visible in the experimental bremsstrahlung spectra of the emitted photons which accompany such a decay. We develop a new formalism of the bremsstrahlung model taking into account the distribution of nucleons in the $\alpha$-decaying nuclear system. We conclude the following. (1) After inclusion of the nucleon structure in the model the calculated bremsstrahlung spectrum is changed very slowly for a majority of the $\alpha$-decaying nuclei. However, we have observed that visible changes really exist for the ${}^{106}\mathrm{Te}$ nucleus ($Q_{\alpha }=4.29$ MeV, $T_{1/2}=70$ μs) even for the energy of the emitted photons up to 1 MeV. This nucleus is a good candidate for future experimental study of this task. (2) Inclusion of the nucleon structure in the model increases the bremsstrahlung probability of the emitted photons. (3) We find the following tendencies for obtaining the nuclei, which have bremsstrahlung spectra more sensitive to the nucleon structure: (a) direction to nuclei with smaller $Z$ and (b) direction to nuclei with larger $Q_{\alpha }$ values.

The dynamic mechanics in the multinucleon transfer reaction ${}^{136}\mathrm{Xe}+{}^{208}\mathrm{Pb}$ at an incident energy of $E_{\mathrm{c}.\mathrm{m}.}=450$ MeV is investigated by using the improved quantum molecular dynamics model (ImQMD). The lifetime of the neck directly influences the nucleon exchange and energy dissipation between the projectile and the target. The total-kinetic-energy–mass distributions and excitation energy division of primary binary fragments and the mass distributions of primary fragments at different impact parameters are calculated. The thermal equilibrium between two reaction partners has been observed at the lifetime of a neck larger than $480\mathrm{fm}/c$. By using the statistical decay code gemini to describe the de-excitation process of the primary fragments, the isotope production cross sections from Pt to At are compared with the prediction by the dinuclear system and GRAZING model. The calculations indicate that the GRAZING model is suitable for estimating the isotope production cross sections only for $\mathrm{\Delta }Z=-1$ to +2; the DNS + gemini calculations underestimate the cross sections in the neutron-rich and neutron-deficient regions; and the ImQMD + gemini calculations give reasonable predictions of the isotope production cross sections for $\mathrm{\Delta }Z=-3$ to 0.

We consider the thermodynamics of excluded-volume particles at finite temperature and chemical potential in the low-density approximation. We assume Boltzmann statistics and study the influence of the excluded volume on an ideal gas thermodynamics at the same temperature, pressure, and number of particles. We show that considering the change of the free enthalpy due to the excluded volume, and using the Maxwell identities, one can derive relevant thermodynamic functions and parameters of multicomponent gases. The derivation is quite general, because particles may have different sizes and shapes which can also depend on their momenta. Besides its simplicity and generality, our approach has the advantage of eliminating the transcendental equations occurring in earlier studies. A representative example of the excluded-volume thermodynamics is the single-component gas of hard spheres. For this case, using a virial expansion, the validity limits of the low-density approximation are also discussed.

We use photoproduction of $\omega$ mesons off complex nuclei to study interactions of transversely and longitudinally polarized vector mesons with nucleons. Whereas the total cross section for interactions of the transversely polarized vector mesons with nucleons ${\sigma }_T=\sigma \left(V_{T}N\right)$ can be obtained from coherent photoproduction, measurements of vector meson photoproduction in the incoherent region provide a unique opportunity to extract the yet unmeasured total cross section for longitudinally polarized mesons ${\sigma }_L=\sigma \left(V_{L}N\right)$. The predictions for the latter strongly depend on the theoretical approaches. This work is stimulated by the construction of the new experiment GlueX at Jefferson Lab, designed to study the photoproduction of mesons in the beam energy range between 5 and 12 GeV.

We study the relation between elliptic flow, $v_2$, and the initial eccentricity, ${\varepsilon }_2$, in heavy-ion collisions, using hydrodynamic simulations. Significant deviations from linear eccentricity scaling are seen in more peripheral collisions. We identify the mechanism responsible for these deviations as a cubic response, which we argue is a generic property of the hydrodynamic response to the initial density profile. The cubic response increases elliptic flow fluctuations, thereby improving agreement of initial condition models with experimental data.

Background: Atomic nuclei often exhibit collective rotational-like behavior in highly excited states, well above the particle emission threshold. What determines the existence of collective motion in the continuum region is not fully understood.

Purpose: In this work, by studying the collective rotation of the positive-parity deformed configurations of the one-neutron halo nucleus ${}^{11}\mathrm{Be}$, we assess different mechanisms that stabilize collective behavior beyond the limits of particle stability.

Method: To solve a particle-plus-core problem, we employ a nonadiabatic coupled-channel formalism and the Berggren single-particle ensemble, which explicitly contains bound states, narrow resonances, and the scattering continuum. We study the valence-neutron density in the intrinsic rotor frame to assess the validity of the adiabatic approach as the excitation energy increases.

Results: We demonstrate that collective rotation of the ground band of ${}^{11}\mathrm{Be}$ is stabilized by (i) the fact that the $\ell =0$ one-neutron decay channel is closed, and (ii) the angular momentum alignment, which increases the parentage of high-$\ell$ components at high spins; both effects act in concert to decrease decay widths of ground-state band members. This is not the case for higher-lying states of ${}^{11}\mathrm{Be}$, where the $\ell =0$ neutron-decay channel is open and often dominates.

Conclusion: We demonstrate that long-lived collective states can exist at high excitation energy in weakly bound neutron drip-line nuclei such as ${}^{11}\mathrm{Be}$.

The centrality dependence of forward jet production in $pA$ collisions at the Large Hadron Collider (LHC) has been found to grossly violate the Glauber model prediction in a way that depends on the $x$ in the proton. We argue that this modification pattern provides the first experimental evidence for $x$-dependent proton color fluctuation effects. On average, parton configurations in the projectile proton containing a parton with large $x$ interact with a nuclear target with a significantly smaller than average cross section and have smaller than average size. We implement the effects of fluctuations of the interaction strength and, using the ATLAS analysis of how hadron production at backward rapidities depends on the number of wounded nucleons, make quantitative predictions for the centrality dependence of the jet production rate as a function of the $x$-dependent interaction strength $\sigma \left(x\right)$. We find that $\sigma \left(x\right)\sim 0.6〈\sigma 〉$ gives a good description of the data at $x=0.6$. These findings support an explanation of the European Muon Collaboration effect as arising from the suppression of small-size nucleon configurations in the nucleus.

Background: Neutron-rich, even-mass chromium and iron isotopes approaching neutron number $N=40$ have been important benchmarks in the development of shell-model effective interactions incorporating the effects of shell evolution in the exotic regime. Odd-mass manganese nuclei have received less attention, but provide important and complementary sensitivity to these interactions.

Purpose: We report the observation of two new $\gamma$-ray transitions in ${}^{63}\mathrm{Mn}$, which establish the $\left(9/2^{-}\right)$ and $\left(11/2^{-}\right)$ levels on top of the previously known $\left(7/2^{-}\right)$ first-excited state. The lifetime for the $\left(7/2^{-}\right)$ and $\left(9/2^{-}\right)$ excited states were determined for the first time, while an upper limit could be established for the $\left(11/2^{-}\right)$ level.

Method: Excited states in ${}^{63}\mathrm{Mn}$ have been populated in inelastic scattering from a ${}^9\mathrm{Be}$ target and in the fragmentation of ${}^{65}\mathrm{Fe}$. $\gamma \gamma$ coincidence relationships were used to establish the decay level scheme. A Doppler line-shape analysis for the Doppler-broadened $(7/2^{-})\to 5/2^{-}$, $\left(9/2^{-}\right)\to (7/2^{-}),$ and $\left(11/2^{-})\to (9/2^{-}\right)$ transitions was used to determine (limits for) the corresponding excited-state lifetimes.

Results: The low-lying level scheme and the excited-state lifetimes were compared with large-scale shell-model calculations using different model spaces and effective interactions in order to isolate important aspects of shell evolution in this region of structural change.

Conclusions: While the theoretical $(7/2^{-})$ and $\left(9/2^{-}\right)$ excitation energies show little dependence on the model space, the calculated lifetime of the $(7/2^{-})$ level and calculated energy of the $\left(11/2^{-}\right)$ level reveal the importance of including the neutron $g_{9/2}$ and $d_{5/2}$ orbitals in the model space. The LNPS effective shell-model interaction provides the best overall agreement with the new data.

We investigate spherical proton emitters in the region from I $\left(Z=53\right)$ to Bi $\left(Z=83\right)$ isotopes as a crucial application of the relativistic energy density functional PC-PK1 beyond the drip line. The continuum effect is treated carefully by using the relativistic continuum Hartree-Bogoliubov theory. We calculate the half-lives of the proton emitters using the Wentzel-Kramers-Brillouin (WKB) method and observe that the calculated values are in reasonable agreement with experimental results for most of emitters considered in this study. We also discuss a clue to improve the functional PC-PK1 in future.

We propose a methodology to calculate microscopically the mass and charge distributions of spontaneous fission yields. We combine the multidimensional minimization of collective action for fission with stochastic Langevin dynamics to track the relevant fission paths from the ground-state configuration up to scission. The nuclear potential energy and collective inertia governing the tunneling motion are obtained with nuclear density functional theory in the collective space of shape deformations and pairing. We obtain a quantitative agreement with experimental data and find that both the charge and mass distributions in the spontaneous fission of ${}^{240}\mathrm{Pu}$ are sensitive both to the dissipation in collective motion and to adiabatic fission characteristics.

The nature of the nuclear pairing condensate is an active topic of investigation, especially as regards its neutron-proton versus identical-particle character, which manifests as the difference between spin-singlet and spin-triplet pairing. In this work, we probe the recently proposed mixed-spin pairing condensates, using a phenomenological Hamiltonian and Hartree-Fock-Bogoliubov theory along with the gradient method. In addition to improving the solution of the many-body problem, we have calculated a series of physical quantities and examined the robustness of the mixed-spin pairing state as the input Hamiltonian is modified. Overall, we find that even though the mixed-spin correlation energy is suppressed in comparison to earlier work, the new pairing behavior persists. We also discuss the possibility of directly probing the mixed-spin pairing phase.

Background: Very neutron-rich isotopes, including ${}^{30-32}\mathrm{Ne}$, in the vicinity of $N=20$ are known to exhibit ground states dominated by $fp$-shell intruder configurations: the “island of inversion.” Systematics for the Ne-isotopic chain suggest that such configurations may be in strong competition with normal shell-model configurations in the ground state of ${}^{29}\mathrm{Ne}$.

Purpose: A determination of the structure of ${}^{29}\mathrm{Ne}$ is thus important to delineate the extent of the island of inversion and better understand structural evolution in neutron-rich Ne isotopes. This is accomplished here through a combined investigation of nuclear and Coulomb-induced one-neutron removal reactions.

Method: Cross sections for one-neutron removal on carbon and lead targets and the parallel momentum distribution of the ${}^{28}\mathrm{Ne}$ residues from the carbon target are measured at around 240 MeV/nucleon. The measurements are compared with reaction calculations combined with spectroscopic information from SDPF-M shell-model wave functions.

Results: The deduced width of the inclusive parallel momentum distribution, 98(12) MeV/$c$ (FWHM), suggests that the ground state of ${}^{29}\mathrm{Ne}$ has a spin parity of $3/2^{-}$. Detailed comparisons of the measured inclusive and partial cross sections of the two targets and the parallel momentum distribution of the carbon target with reaction calculations, combined with spectroscopic information from large-scale shell-model calculations, are all consistent with a $3/2^{-}$ spin-parity assignment.

Conclusions: The results indicate that ${}^{29}\mathrm{Ne}$ lies within the island of inversion and that the ground state of ${}^{29}\mathrm{Ne}$ is dominated by a ${}^{28}\mathrm{Ne}\left(0_1^{+}\right)\otimes 2p_{3/2}$ neutron configuration. Combined with recently measured interaction cross sections, it is concluded that ${}^{29}\mathrm{Ne}$ may exhibit a moderately developed halo-like distribution.

The ${}^{76}\mathrm{Ge}$(n,p)${}^{76}\mathrm{Ga}$ reaction and the subsequent $\beta$ decay of ${}^{76}\mathrm{Ga}$ to ${}^{76}\mathrm{Ge}$ has been used to excite the 3951.89-keV state of ${}^{76}\mathrm{Ge}$, which decays by the emission of a 2040.70-keV $\gamma$ ray. Using high-purity germanium detectors, the associated pulse-height signal may be undistinguishable from the potential signal produced in neutrinoless double-$\beta$ decay of ${}^{76}\mathrm{Ge}$ with its $Q$ value of 2039.0 keV. At 20-MeV neutron energy the production cross section of the 2040.70-keV $\gamma$ ray is approximately 0.1 mb.

Complete fusion excitation functions of reactions involving breakup are studied by using the empirical coupled-channel (ECC) model with breakup effects considered. An exponential function with two parameters is adopted to describe the prompt-breakup probability in the ECC model. These two parameters are fixed by fitting the measured prompt-breakup probability or the complete fusion cross sections. The suppression of complete fusion at energies above the Coulomb barrier is studied by comparing the data with the predictions from the ECC model without the breakup channel considered. The results show that the suppression of complete fusion is roughly independent of the target for the reactions involving the same projectile.

We show that critical systems of finite size develop a fractal structure in momentum space with anomalous dimension given in terms of the isotherm critical exponent $\delta$ of the corresponding infinite system. The associated power laws of transverse momentum correlations, in high-energy nuclear collisions, provide us with a signature of a critical point in strongly interacting matter according to the laws of QCD.