High-energy γ rays from the decay of the giant-dipole resonance built on excited states were measured in coincidence with fission fragments for the reaction ${}^{19}{\mathrm{F}+}^{181}{\mathrm{T}\overrightarrow{a}}^{200}\mathrm{Pb}$ at bombarding energies 161 and 181 MeV. The γ-ray spectra containing contributions from the decay of the hot compound ${}^{200}\mathrm{Pb}$ nucleus on its way to fission and from the decay of the fission fragments were analyzed using the statistical model modified to include the effects of nuclear dissipation. Calculations with nuclear viscosity parameter of ${\gamma }_i=3\mathrm{}$ inside the saddle point and ${\gamma }_o=10\mathrm{}$ for the saddle to scission decay describe the experimental data.

We compute bremsstrahlung arising from the acceleration of individual charged baryons and mesons during the time evolution of high-energy $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at the Relativistic Heavy Ion Collider using a microscopic transport model. We elucidate the connection between bremsstrahlung and charge stopping by colliding artificial pure proton on pure neutron nuclei. From the intensity of low energy bremsstrahlung, the time scale and the degree of stopping could be accurately extracted without measuring any hadronic observables.

We evaluate the operator product expansion (OPE) for a mixed correlator of the isovector and isoscalar vector currents in the background of the nucleon density with intrinsic isospin asymmetry (i.e., excess of neutrons over protons) and match it with its imaginary part, given by resonances and continuum, via the dispersion relation. The leading density-dependent contribution to $\rho -\omega$ mixing is due to the scattering term, which turns out to be larger than any density dependent piece in the OPE. We estimate that the asymmetric density of $n_n-n_p\sim 2.5\times {10}^{-2}{\mathrm{fm}}^{-3}$ induces the amplitude of $\rho -\omega$ mixing, equal in magnitude to the mixing amplitude in vacuum, with the constructive interference for positive and destructive for negative values of $n_n-n_p.$ We revisit sum rules for vector meson masses at finite nucleon density to point out the numerical importance of the screening term in the isoscalar channel, which turns out to be one order of magnitude larger than any density-dependent condensates over the Borel window. This changes the conclusions about the density dependence of $m_{\omega },$ indicating $\sim 40\mathrm{MeV}$ increase at nuclear saturation density.

Within the relativistic mean-field theory, we reinvestigate the Dautry-Nyman instability of the normal many-particle state in the linear sigma model (LσM). It is shown that an “instability” due to an inappropriate quantization of Dirac field inheres in the normal state of LσM. Then we see that, in a wide class of models which are compatible with the nuclear-matter data at saturation, there generally exists a critical density above which a condensation of σ and ${\pi }^0$ with a finite wave vector takes place. It has been known that the coupling of wave vector to nucleon spin causes the dispersion relation of nucleons to dissolve into two distinct branches. In case one of these branches lies sufficiently lower than the normal branch, the phase with $\sigma {\pi }^0$ condensation emerges with strong spin polarizations.

Properties of the collective bands in ${}^{125}\mathrm{I},$ populated in ${}^{123}\mathrm{Sb}(\alpha ,2n\gamma {)}^{125}\mathrm{I}$ reaction at $E=30\mathrm{}\hspace{0.5em}\mathrm{MeV},$ have been studied from $\gamma$-ray angular distributions and excitation functions. Spins and parities are inferred for several states. New $E2/M1\mathrm{}$ mixing ratios are deduced for five transitions. A three-quasiparticle collective band is proposed on the basis of these and earlier results. The shapes of the ground state yrast band and the $g_{9/2}$ band are discussed, providing evidence for the coexistence of prolate and oblate collective states.

The reflection asymmetric shell model has been established by means of the variational procedure and the projection method to describe the high spin states of octupole deformed nuclei. The $Q\cdot Q$ forces of quadrupole, octupole, and hexadecapole as well as the monopole and quadrupole pairings are included in the Hamiltonian. The shell model space is spanned by a selected set of the simultaneous angular momentum- and parity-projected BCS multiquasiparticle states which are intrinsically deformed. The general features of rotational octupole bands in even-even nuclei can be interpreted and reproduced by the present model, and the calculated results for the Ra isotopes are in good agreement with the experimental data.

The structure of deformed proton emitters is studied in a coupled-channels treatment. The wave function of a decaying state is determined as a standing wave, i.e., for an energy that is real. The decay rate is calculated from a Green’s function method, treating the influence of the long-range Coulomb multipole interactions to first order. The results are compared to predictions made in the adiabatic limit and to measurements. It is shown that the decay of the ${}^{131}\mathrm{Eu}{(3/2\mathrm{}}^{+})$ ground state to the ground state of ${}^{130}\mathrm{Sm}$ is quite sensitive to deformation in the spin-orbit force. It is found that the ground state decay of ${}^{141}\mathrm{Ho}{(7/2\mathrm{}}^{-})$ is poorly described in the coupled-channels approach. This is ascribed to Coriolis mixing, which is too strong in the absence of pairing effects.

We propose a novel method to study quantum-classical correspondence in complex, e.g., heavy-ion, atomic, molecular, and atomic cluster collisions. The many-body rotating wave packets are formed spontaneously and their stability is due to the slow decoherence between highly excited strongly overlapping states of the intermediate complex. The phenomenon is illustrated by analyzing the ${}^{12}{\mathrm{C}+}^{24}\mathrm{Mg}$ collision. The significant deviations from the random-matrix theory are reproduced in terms of the macroscopically rotating molecule formed in this collision.

Starting from a pointlike two- and three-particle interaction the kinetic equation is derived. While the drift term of the kinetic equation turns out to be determined by the known Skyrme mean field the collision integral appears in two- and three-particle parts. The cross section results from the same microscopic footing and is naturally density dependent due to the three-particle force. By this way no hybrid model for drift and cross section is needed for nuclear transport. Besides the mean field correlation energy the resulting equation of state also has a two- and three-particle correlation energy which are both calculated analytically for the ground state. These energies contribute to the equation of state and lead to an occurrence of a maximum at three times nuclear density in the total energy.

Energy spectra and angular distributions of protons emitted from the inclusive $\mathrm{}(d,xp)\mathrm{}$ reaction on ${}^9\mathrm{Be},$ ${}^{12}\mathrm{C},$ ${}^{27}\mathrm{Al},$ ${}^{58}\mathrm{Ni},$ ${}^{93}\mathrm{Nb},$ ${}^{181}\mathrm{Ta},$ ${}^{208}\mathrm{Pb},$ and ${}^{238}\mathrm{U}$ were measured at an incident deuteron energy of 100 MeV. The protons were detected at laboratory scattering angles of $6°$ to $120°$ and $8°$ to $120°$ for the targets with $9<~A<~27$ and $A>~58,$ respectively. Two triple-element and three double-element detector telescopes allowed for a low energy detection threshold of 4 to 8 MeV. The experimental results are presented in double-differential as well as angle- and energy-integrated cross sections. For all the nuclei studied, the energy spectra at forward angles show pronounced deuteron breakup peaks centered around approximately half of the incident deuteron energy. Qualitatively the energy spectra are similar for all nuclei at a given angle except in the region of the low-energy evaporation peak. As a function of target mass the evaporation cross sections are found to increase up to $A=58\mathrm{}$ after which they decrease again. The total preequilibrium proton cross section is roughly $(280\mathrm{}\pm {60)A}^{1/3}\hspace{0.5em}\mathrm{mb}.$ The angular distributions at the high emission energies are strongly forward peaked while the distributions of the low-energy protons are almost isotropic. The LAHET code system (LCS) was applied to calculate the proton production cross sections. Standard LCS calculations are found to underpredict the experimental cross sections at the very forward angles on the heavy target nuclei $\left(A\gtrsim 58\right).$ By adding incoherently the Coulomb breakup cross section of the deuteron to the LCS calculations the experimental cross sections are reproduced to within 10%. Although preequilibrium processes are a necessary ingredient in the LCS calculations of the large-angle cross sections, this code still fails to predict the experimental evaporation distributions.

Applying heavy-baryon chiral perturbation theory to ordinary muon capture (OMC) on a proton, we calculate the capture rate and neutron helicity asymmetry up to next-to-next-to-leading order. For the singlet hyperfine state, we obtain the capture rate ${\Gamma }_0=695\mathrm{}$ ${\mathrm{s}}^{-1}$ while, for the triplet hyperfine state, we obtain the capture rate ${\Gamma }_1=11.9\mathrm{}$ ${\mathrm{s}}^{-1}$ and the neutron asymmetry ${\alpha }_1=\mathrm{0.93.}\mathrm{}$ If the existing formalism is used to relate these atomic capture rates to ${\Gamma }_{\mathrm{liq}},$ the OMC rate in liquid hydrogen, then ${\Gamma }_{\mathrm{liq}}$ corresponding to our improved values of ${\Gamma }_0$ and ${\Gamma }_1$ is found to be significantly larger than the experimental value, primarily due to the updated larger value of $g_A.$ We argue that this apparent difficulty may be correlated to the specious anomaly recently reported for ${\mu }^{-}+\overrightarrow{p}n+{\nu }_{\mu }+\gamma ,$ and we suggest a possibility to remove these two “problems” simply and simultaneously by reexamining the molecular physics input that underlies the conventional analysis of ${\Gamma }_{\mathbf{liq}}.$

We investigate the structure of the neutron rich nucleus ${}^{14}\mathrm{B}$ through studies of its breakup in the Coulomb field of a heavy target. The breakup amplitude is calculated within an adiabatic as well as finite range distorted wave Born approximation theories of breakup reactions. Both these formalisms allow the use of realistic wave functions for the relative motion between the fragments in the ground state of the projectile. The longitudinal momentum distributions of ${}^{13}\mathrm{B}$ (ground state) following the breakup of ${}^{14}\mathrm{B}$ on a heavy target at beam energy of 60 MeV/nucleon, calculated using two possible ground state configurations of ${}^{14}\mathrm{B},$ have been compared with the recent data. The data seem to favor ${}^{13}\mathrm{B}\left({\frac{3}{2}}^{-}\right)\otimes {2s}_{1/2}$ as the possible ground state configuration of ${}^{14}\mathrm{B}$ with a spectroscopic factor close to unity. We give our predictions for the exclusive neutron angular distributions and the relative energy spectra in the one-neutron removal reaction of ${}^{14}\mathrm{B}.$

A critical analysis of the cross sections for the characteristic $\gamma$ rays of the residual nuclei following ${}^6\mathrm{Li}{+}^{16}\mathrm{O}$ and ${}^7\mathrm{Li}{+}^{16}\mathrm{O}$ reactions shows that if the breakup mechanism is supposed to be responsible for the limitation of fusion cross sections for these systems, then the large magnitude of the cross sections for the $\gamma$ rays cannot be accounted for.

The first excited state in the neutron-rich N=20 isotope ${}^{31}\mathrm{Na}$ was observed at 350(20) keV via intermediate energy heavy-ion scattering, which is dominated by the Coulomb excitation mechanism. This state appears to be a rotational excitation built on a strongly deformed ground state. The yield of the γ ray deexciting this state can be reproduced by a shell model calculation which takes $\nu {(f}_{7/2}{,p}_{3/2})$ intruder configurations into account.

Cross sections for the ${}^3\mathrm{He}{(e,e}^{\prime }pp)n$ reaction were measured over a wide range of energy and three-momentum transfer. At a momentum transfer $q=375\mathrm{}\mathrm{MeV}/c,$ data were taken at transferred energies $\omega$ ranging from 170 to 290 MeV. At $\omega =220\mathrm{}\mathrm{MeV},$ measurements were performed at three q values (305, 375, and $445\mathrm{MeV}/c).\mathrm{}$ The results are presented as a function of the neutron momentum in the final state, as a function of the energy and momentum transfer, and as a function of the relative momentum of the two-proton system. The data at neutron momenta below $100\mathrm{MeV}/c,$ obtained for two values of the momentum transfer at $\omega =220\mathrm{}\mathrm{MeV},$ are well described by the results of continuum-Faddeev calculations. These calculations indicate that the cross section in this domain is dominated by direct two-proton emission induced by a one-body hadronic current. Cross section distributions determined as a function of the relative momentum of the two protons are fairly well reproduced by continuum-Faddeev calculations based on various realistic nucleon-nucleon potential models. At higher neutron momentum and at higher energy transfer, deviations between data and calculations are observed that may be due to contributions of isobar currents.

We have recently proposed a method to select core and cluster in a binary component description of atomic nuclei. The choice is based on the mismatch between measured binding energies and the underlying trend supplied by the liquid drop model. A key point is that the charge to mass ratios of parent, core, and cluster should be as nearly equal as possible. This approach implies that superdeformation should be ubiquitous across the Periodic Table. In these binary models, the transition quadrupole moments $Q_t$ of superdeformed (SD) bands depend strongly on the charge and mass splits, but are rather insensitive to other details. In fact, given the cluster charge $〈Z_2〉,$ $Q_t$ can be determined algebraically. We compare calculations of transition quadrupole moments with the measured values for the 41 SD bands in 21 even-even nuclei for which experimental data are available. The mass range is from $A\sim 60$ to $A\sim 240$ and the values of $Q_t$ vary from $\sim 3\hspace{0.5em}e\mathrm{b}$ to $\sim 30\hspace{0.5em}e\mathrm{b}.$ A good level of agreement is obtained.

Differential cross sections for 7.5 MeV neutron scattering from ${}^{140,142}\mathrm{Ce}$ have been measured and analyzed in conjunction with previously known total cross sections between 0.5 and 10 MeV and scattering properties in the very low-energy or resonance region. The differential elastic scattering cross sections, total cross sections, and resonance-region properties enable us to fix the mean scattering fields, so that the scattering amplitudes at the nuclear surface are given with confidence. The inelastic scattering cross sections are then analyzed to extract the excitation strengths of a few collective levels. The level-excitation strengths found in this neutron scattering analysis provide insight into the $4_1^{+}$ level’s configuration, and also have been compared to strengths observed in electron scattering and Coulomb excitation to separate the roles of protons and neutrons in $2^{+},$ $3^{-},$ and $4^{+}$ levels excited in ${}^{140}\mathrm{Ce}.$

A high-resolution measurement of fragment-fragment-$\gamma$ triple coincidence events in the symmetric and near-symmetric mass exit channels from the ${}^{28}\mathrm{Si}{+}^{28}\mathrm{Si}$ reaction has been undertaken using the EUROGAM Phase II $\gamma$-ray spectrometer. The bombarding energy of $E_{\mathrm{lab}}{(}^{28}\mathrm{Si})=111.6\mathrm{}\hspace{0.5em}\mathrm{MeV}$ has been selected to populate the conjectured $J^{\pi }{=38\mathrm{}}^{+}$ quasimolecular resonance in the ${}^{56}\mathrm{Ni}$ dinuclear system. In the ${}^{28}\mathrm{Si}{+}^{28}\mathrm{Si}$ symmetric mass exit channel, the resonance behavior is clearly verified at the chosen energy. The population of highly excited states in the ${}^{24}\mathrm{Mg},$ ${}^{28}\mathrm{Si},$ and ${}^{32}\mathrm{S}$ nuclei is discussed within a statistical fusion-fission model. Evidence is presented for selective population of states in the ${}^{28}\mathrm{Si}$ fragments arising from the symmetric fission of the ${}^{56}\mathrm{Ni}$ compound nucleus. The enhanced population of the $K^{\pi }{=3\mathrm{}}_1^{-}$ band of the ${}^{28}\mathrm{Si}$ nucleus, indicative of an oblate deformed shape, suggests that the oblate configuration plays a significant role in the resonant process. Fragment angular distributions for the elastic and low-lying inelastic channels as well as $\gamma$-ray angular correlations for the mutual inelastic channel ${(2\mathrm{}}^{+}{,2\mathrm{}}^{+})$ indicate that the spin orientations of the outgoing fragments are perpendicular to the orbital angular momentum. This unexpected result, which is different from the alignment found for the resonance structures in the ${}^{24}\mathrm{Mg}{+}^{24}\mathrm{Mg}$ and ${}^{12}\mathrm{C}\mathrm{}{+}^{12}\mathrm{C}$ systems, suggests a situation where two oblate ${}^{28}\mathrm{Si}$ nuclei interact in an equator-to-equator stable molecular configuration. A discussion concerning the spin alignment and spin disalignment for different reactions such as ${}^{12}\mathrm{C}\mathrm{}{+}^{12}\mathrm{C},$ ${}^{24}\mathrm{Mg}{+}^{24}\mathrm{Mg},$ and ${}^{28}\mathrm{Si}{+}^{28}\mathrm{Si}$ is presented.

Previously unidentified states in the neutron-rich nucleus ${}^{194}\mathrm{Os}$ have been populated following a deep inelastic reaction using a 780 MeV ${}^{136}\mathrm{Xe}$ beam on a thick ${}^{198}\mathrm{Pt}$ target. $\gamma -\gamma$ coincidence events were collected using the $8\pi$ detector array. The yrast band in ${}^{194}\mathrm{Os}$ has been observed up to $I^{\pi }{=(10\mathrm{}}^{+}),$ for the first time. This represents the heaviest osmium nucleus where in-beam γ-ray spectroscopy has been performed to date. The excitation energies of the new levels are compared to the systematics of the lighter even-even osmium nuclei. The evidence for a transition from prolate to oblate-deformed ground states in the heavy osmium nuclei is discussed and total Routhian surface calculations are presented. An alignment analysis together with cranked shell model calculations, suggest that the yrast states have a prolate shape, in contrast to earlier interpretations. Predictions for the neighboring even-even tungsten isotopes are also described.

The spin-dependent neutron-proton total cross-section differences $\Delta {\sigma }_L$ and $\Delta {\sigma }_T$ have been measured between $E_n=5\mathrm{}$ and 20 MeV in longitudinal and transverse nucleon spin orientations. From these data the ${}^3{S}_1{-}^3{D}_1$ mixing parameter ${\varepsilon }_1,$ which characterizes the nucleon-nucleon tensor force at low and intermediate energies, was determined in a model-insensitive way. In combination with measurements at higher energies, our values for ${\varepsilon }_1$ support a nucleon-nucleon tensor interaction that is stronger than predicted by all modern high-precision nucleon-nucleon potential models and phase-shift analyses.