The electric form factor of the neutron $G_{E,n}$ has been measured in the quasifree ${}^2\mathrm{H}\left(\overrightarrow{e}{,e}^{\prime }\overrightarrow{n}\right)p$ reaction using the 855 MeV polarized cw electron beam of the Mainz Microtron MAMI. The polarization of the scattered neutrons was analyzed in a polarimeter consisting of two walls of plastic scintillators. The precession of the neutron spin in a magnetic field was used for the first time to circumvent the measurement of the effective analyzing power of the polarimeter and the beam polarization. In this way $G_{E,n}$ could be determined with little model dependence and experimental uncertainties. The result $G_{E,n}\left(0.34\mathrm{GeV}{}^2/c^2\right)=0.0611\mathrm{}\pm {0.0069}_{\mathrm{stat}}(\{+0.0069\mathrm{}\}\{-0.0055\mathrm{}\}{)}_{\mathrm{syst}}$ is larger than previously assumed.

Using the spectral function ${\phi }^{\prime }\left(z\right)/\phi \left(z\right)$, the random-phase approximation correlation energy and other properties of a finite system can be written as a contour integral in a compact way. This yields a transparent expression and reduces drastically the numerical efforts for obtaining reliable values. For illustration the method is applied to pairing vibrations in rotating nuclei.

The ${}^{17}\mathrm{F}(p,\gamma {)}^{18}\mathrm{Ne}$ reaction is important in stellar explosions, but its rate has been uncertain because of an expected $3^{+}$ state in ${}^{18}\mathrm{Ne}$ that has never been conclusively observed. This state would provide a strong $\ell =0\mathrm{}$ resonance and, depending on its excitation energy, could dominate the stellar reaction rate. We have observed this missing $3^{+}$ state by measuring the ${}^1\mathrm{H}{(}^{17}\mathrm{F},p{)}^{17}\mathrm{F}$ excitation function with a radioactive ${}^{17}\mathrm{F}$ beam at the ORNL Holifield Radioactive Ion Beam Facility. We find that the state lies at a center-of-mass energy of $E_r=599.8\mathrm{}\pm 1{.5}_{\mathrm{stat}}\pm {2.0}_{\mathrm{sys}}\mathrm{keV}$ ( $E_x=4523.7\mathrm{}\pm 2.9\mathrm{keV}$) and has a width of $\Gamma =18\mathrm{}\pm 2_{\mathrm{stat}}\pm 1_{\mathrm{sys}}\mathrm{keV}$.

The magnitudes and relative phase of the $E2\mathrm{}$ and $M1\mathrm{}$ electron scattering form factors of the 6.32 MeV ( ${\frac{3}{2}}^{-}$) state of ${}^{15}\mathrm{N}$ have been measured at momentum transfers ( $q$) of 0.63 and $1.07{\mathrm{fm}}^{-1\mathrm{}}$. These two transverse multipole form factors were separated using a combined analysis of single-arm $\left({e,e}^{\prime }\right)$ and coincident $\left({e,e}^{\prime }\gamma \right)$ data. This measurement is the first model independent separation of multipole form factors that contribute to a mixed transition.

A superdeformed rotational structure is reported in the stable nucleus ${}^{68}\mathrm{Zn}$. It has a transition quadrupole moment ( $Q_t$) of ${2.5}_{-0.4\mathrm{}}^{+0.7\mathrm{}}$ $e$ b ( ${\beta }_2\approx 0.4$), as measured by the residual Doppler shift method. Theoretical calculations suggest that two different configurations are possible candidates for this band. One is built without $h_{11/2}$ neutrons, as seen in superdeformed bands in the $A\sim 60$ region, while the other involves one $h_{11/2}$ neutron in analogy with superdeformed bands in the $A\sim 80$ region. The second of these candidate configurations is preferred, thus establishing a new, neutron-rich (relative to the line of $\beta$ stability) region of superdeformation with $Z\sim 30$ and $N\sim 38$.

Electron scattering form factors for transitions between low-lying states of ${}^{24}\mathrm{Mg}$ are calculated in the symplectic shell model. It is shown that multi- $ħ\omega$ correlations contribute in a very substantial but complex manner to nuclear current and charge densities. Implications for using scattering data to extract limits on contributions from subnucleonic effects are considered.

We report on the first measurement of spin-correlation parameters in quasifree electron scattering from vector-polarized deuterium. Polarized electrons were injected into an electron storage ring at a beam energy of 720 MeV. A Siberian snake was employed to preserve longitudinal polarization at the interaction point. Vector-polarized deuterium was produced by an atomic beam source and injected into an open-ended cylindrical cell, internal to the electron storage ring. The spin correlation parameter $A_{\mathrm{ed}}^V$ was measured for the reaction ${}^2\overrightarrow{\mathrm{H}}\left(\overrightarrow{e}{,e}^{\prime }n\right)p$ at a four-momentum transfer squared of 0.21 $(\mathrm{GeV}/c{)}^2$ from which a value for the charge form factor of the neutron was extracted.

The chiral two-pion exchange component of the long-range $\mathrm{pp}$ interaction is studied in an energy-dependent partial-wave analysis. We demonstrate its presence and importance and determine the chiral parameters $c_i$ ( $i=1,3,4\mathrm{}$). The values agree well with those obtained from pion-nucleon amplitudes.

Two-neutron transfer reactions induced by the Borromean nucleus ${}^6\mathrm{He}$ on ${}^4\mathrm{He}$ and ${}^1\mathrm{H}$ targets are analyzed within a realistic four-body model. Available experimental data are well described, and it is the “di-neutron” configuration of the ${}^6\mathrm{He}$ nucleus that is found to make the dominant contribution to the cross sections of the two-neutron transfer reactions.

The study of spherical-deformed ground-state phase transitions in finite nuclei as a function of $N$ and $Z$ is hindered by the discrete values of the nucleon number. A resolution of the integer nucleon number problem and evidence relating to phase transitions in finite nuclei are discussed from the experimental point of view and interpreted within the framework of the interacting boson model.

A strong differential transverse collective flow is predicted for the first time to occur in heavy-ion collisions at balance energies. We also give a novel explanation for the disappearance of the total transverse collective flow at the balance energies. It is further shown that the differential flow especially at high transverse momenta is a useful microscope capable of resolving the balance energy's dual sensitivity to both the nuclear equation of state and in-medium nucleon-nucleon cross sections in the reaction dynamics.

A novel mechanism of nuclear fragmentation is proposed. Assuming microcanonical equilibrium, it is shown that a strong enhancement of the accessible volume of the phase space due to the diffuseness of nuclear surface leads to dynamical instabilities of hot nuclei and to a fragmentation. Equations are derived for the transition temperature $T_T$ for which the thermodynamical surface tension vanishes, as well as for the thermodynamical fissility parameter ${\chi }_{\mathrm{td}}$.

Fission times of uraniumlike nuclei with excitation energies up to about 250 MeV have been inferred from blocking effects in a single crystal. They are found longer by at least 1 order of magnitude than the ones obtained by other techniques, a hint for very broad fission time distributions.

Proton-proton bremsstrahlung cross sections have been measured at 389 MeV incident energy. A two-arm spectrometer and a liquid hydrogen target system have been used to measure the proton-proton bremsstrahlung events with small background. At the present kinematical conditions, an enhancement of the cross sections due to the $\Delta$ current contribution is predicted. The measured cross sections are larger than the theoretical predictions including the $\Delta$ current contribution.

Nonequilibrium features of a first order phase transition from the quark-gluon plasma to a hadronic gas in relativistic heavy-ion collisions are discussed. It is demonstrated that strong collective expansion may lead to the fragmentation of the plasma phase into droplets surrounded by undersaturated hadronic gas. Subsequent hadronization of droplets will generate strong nonstatistical fluctuations in the hadron rapidity distribution in individual events. The strongest fluctuations are expected in the vicinity of the phase transition threshold.

Spectroscopic studies of the $\beta$ decay of ${}^{140}\mathrm{I}$ have firmly established octupole collectivity in ${}^{140}\mathrm{Xe}$ and evinced unique theoretical predictions of a quenched dipole moment. The first detailed investigations of an exotic Xe nucleus, including measurements of half-lives of levels in the ground and octupole bands, were made possible due to a new approach to produce beams of iodine with ISOL sources.

A detailed quantitative experimental investigation of the influence of nuclear deformation on the angular distribution of $\alpha$ particles emitted by oriented nuclei is reported. The favored $\alpha$ transitions in the decay of the deformed nuclei ${}^{221}\mathrm{Fr}$, ${}^{227}\mathrm{Pa}$, and ${}^{229}\mathrm{Pa}$ were studied. In all three cases, very large anisotropies have been observed. The results are in good agreement with calculations based on $\alpha$ particle tunneling through a deformed Coulomb barrier.

Measurements of polarization observables are presented for the $p-d$ radiative capture reaction. A new analysis technique, based on Watson's theorem, is used to extract the reaction matrix elements. The new method allows one to fix the phases of the matrix elements by incorporating information from the elastic scattering channel.

Ground-state properties of deformed proton-rich odd- $Z$ nuclei in the region $59\le Z\le 69$ are described in the framework of relativistic Hartree-Bogoliubov (RHB) theory. One-proton separation energies and ground-state quadrupole deformations that result from fully self-consistent microscopic calculations are compared with available experimental data. The model predicts the location of the proton drip-line, the properties of proton emitters beyond the drip-line, and provides information about the deformed single-particle orbitals occupied by the odd valence proton.

We reexamine a symmetry in nucleon-nucleus scattering that previously had been proclaimed to be dead. We show that this symmetry is the continuum analog of pseudospin symmetry, a relativistic symmetry which manifests itself in the spectra of nuclei. Using experimental data only, we show that pseudospin symmetry in nucleon-nucleus scattering is not dead but only modestly broken for 800 MeV proton scattering on nuclei.