High lying excitations consisting of particle-hole plus two-particle two-hole configurations coupled to the continuum are analyzed in ${}^{208}\mathrm{Pb}$. Partial decay widths are calculated and the effect of the two-particle two-hole excitatons upon the widths are assessed. It is found that double giant resonance excitations are not mixed with other degrees of freedom and that double monopole giant resonances are likely to be detected in ${}^{208}\mathrm{Pb}$ by measuring dilepton $\mathrm{}\left(E0\mathrm{}\right)\mathrm{}$ emission.

We show that, within a two-group schematic random phase approximation model, a concentration of local dipole strength in the lower tail region of the electric giant dipole resonance can show up. The model is tested under more realistic circumstances for the isovector 1${}^{-}$ states in ${}^{116}$Sn.

Gamow-Teller decays of $N=51\mathrm{}$ nuclei are calculated, taking into account core polarization corrections. Results are in fair agreement with experiment, but predict much more strength in the decay of ${}^{96}\mathrm{Rh}$ than has been observed experimentally.

A recently proposed fluctuation analysis of resonant photon scattering spectra [J. Enders et al., Phys. Rev. Lett. 79, 2010 (1997)] is applied to the ${}^{157}\mathrm{Gd}(\gamma ,{\gamma }^{\prime })$ reaction. Evidence for unresolved strength in the experimental background is found which amounts to a total dipole excitation strength of $\sum g{\Gamma }_0^{\mathrm{red}}{=(30\mathrm{}}_{-10}^{+6\mathrm{}}){\mathrm{m}\mathrm{e}\mathrm{V}/\mathrm{M}\mathrm{e}\mathrm{V}}^3$ in the excitation energy range 2.5–4 MeV. Assuming a smooth variation of the $M1/E1\mathrm{}$ strength ratio in the neighboring even-mass nuclei, the $M1\mathrm{}$ part can be estimated to be ${B\left(M1\mathrm{}\right)=(2.0\mathrm{}}_{-0.7}^{+0.4\mathrm{}})$ ${\mu }_N^2.$ This value is close to the expectation of sum rules. We discuss possible sources of errors which suggests that the obtained value represents a lower limit only.

Intermediate mass fragments (IMF) and light particles emitted from the ${}^{58}{\mathrm{N}\mathrm{i}+}^{58}\mathrm{Ni}$ reaction at a beam energy of 375 MeV have been studied. The fragments and light particles were measured in coincidence with 4π γ-ray spectrometer. The $Z=6\mathrm{}$ (C) kinetic energy spectra and the distribution of the final nuclei in coincidence with the emitted C are well described by Hauser-Feshbach calculations extended to many channels. A detailed study of C-γ and 3α-γ correlations indicate a strong selectivity of the IMF decay. Our results indicate that the IMF can populate nuclei that are not accessible via multiple light particle $\mathrm{}(Z<\mathrm{}3\mathrm{})\mathrm{}$ emission and, thus, are useful for nuclear structure studies.

Energy spectra have been measured for helium and hydrogen isotopes emitted from highly excited residues produced in central ${}^{129}$Xe + ${}^{\mathrm{nat}}$Cu collisions at $E/A=30\mathrm{}$ MeV. The observed differences between the spectra for ${}^3$He and ${}^4$He nuclei can be attributed to the time dependent evaporative cooling of the residues. This cooling dynamics is also reflected in a characteristic dependence of isotope ratios on the kinetic energy of the emitted particles in reasonable agreement with present evaporative models.

Semi-inclusive proton and pion distributions from central Au+Au reactions at 11.6$A$ GeV/$c$ have been measured. The proton rapidity distribution shows significantly increased stopping compared to lighter systems, providing strong evidence for the formation of a state of matter with baryon density substantially greater than normal nuclear matter. Unlike reactions at this energy induced by lighter heavy ions, at low $m_t-m_0$ the proton invariant spectra deviate from a single exponential shape and become flatter, while ${\pi }^{-}$ spectra are found to rise faster than the ${\pi }^{+}$ spectra.

The high spin level structure of ${}^{98}$Rh has been extended to a spin of 16$ħ$ and excitation energy of 8.3 MeV through the discrete-line $\gamma$-ray spectroscopy. A negative parity rotational band has been observed which exhibits a large signature splitting and a signature inversion at $I=10\mathrm{}ħ$. The particle-rotor model calculations using a β=0.13 and $(\pi g_{9/2}\otimes \nu h_{11/2})$ configuration for the odd proton and neutron give a good description of the above-mentioned characteristics of the band. Thus ${}^{98}$Rh is the nucleus closest to the $N=50\mathrm{}$ shell closure which exhibits a deformed band based on the $h_{11/2}$ intruder orbital.

We have studied the $\beta$-delayed particle decay of ${}^{17}$Ne to test the feasibility of determining both the $E1\mathrm{}$ and $E2\mathrm{}$ components of the ${}^{12}$C$(\alpha ,\gamma {)}^{16}$O cross section at energies relevant to helium burning in stars. In this context we have observed the breakup of the isobaric analog state in ${}^{17}$F at 11.193 MeV into three particles via three channels: proton decay to the 9.59 MeV state in ${}^{16}$O; and $\alpha$ decay to the 2.365 and 3.502/3.547 MeV states in ${}^{13}$N. This is the first reported observation of the decay of the IAS to the $1^{-}$ state in ${}^{16}$O at 9.59 MeV and the first reported $\beta$-delayed proton-$\alpha$ decay. With straightforward improvements to our detection apparatus to improve angular resolution, $\beta$ suppression, and solid angle coverage, we should be able to proceed to the measurement of the effect of the tail of the subthreshold state at 7.117 MeV in ${}^{16}$O on the $\alpha$ spectrum from the breakup of the 9.59 MeV state.

A Hartree-Bose mean-field approximation for the IBM-3 is presented. A Hartree-Bose transformation from spherical to deformed bosons with charge-dependent parameters is proposed which allows bosonic pair correlations and includes higher angular momentum bosons. The formalism contains previously proposed IBM-2 and IBM-3 intrinsic states as particular limits.

The level structure of ${}^{219}\mathrm{Rn}$ has been studied using the alpha decay of ${}^{223}\mathrm{Ra}$ and coincident gamma rays. While only modest changes are required in the level structure, and only above 342.8 keV, severe changes are required throughout the level scheme in the spin assigments. These changes allow the assignment of two sets of anomalous bands with ${K=5/2\mathrm{}}^{\pm }$ and ${K=3/2\mathrm{}}^{\pm }.$ The ${K=5/2\mathrm{}}^{\pm }$ bands have configurations intermediate between the reflection asymmetric configuration and the $g_{9/2}$ shell model configuration, while the ${K=3/2\mathrm{}}^{\pm }$ bands have configurations intermediate between the mixed reflection asymmetric configuration and the $i_{11/2}$ shell model configuration. Comparison of the systematics of ${}^{219}\mathrm{Rn}$ with neighboring isotones, isobars, and isotopes shows clearly the collapse of the quadrupole-octupole-type configurations into the less degenerate shell model configurations.

Lifetimes of a superdeformed band in ${}^{82}$Sr were measured with the centroid shift method. The measured average quadrupole moment of this band corresponds to a quadrupole deformation of ${\beta }_2\approx 0.49$, which is slightly smaller than both the theoretical prediction, and the measured deformation of the SD band in the neighboring isotone ${}^{84}$Zr. Lifetimes of high spin states of three normally deformed rotational bands in ${}^{82}$Sr were also measured with the Doppler shift attenuation method technique. The quadrupole moments of these normally deformed bands show a decrease at the highest spins, supporting the predicted band terminations.

The ${}^{12}\mathrm{C}(\gamma ,pn)$, ${}^{12}\mathrm{C}(\gamma ,pp)$, ${}^{12}\mathrm{C}(\gamma ,ppp)$, ${}^{12}\mathrm{C}(\gamma ,pp{\pi }^{\pm })$, ${}^{12}\mathrm{C}(\gamma ,p{\pi }^{\pm })$ reactions have been studied using tagged photons of energy $E_{\gamma }=250\mathrm{}$–600 MeV. A model which includes all major absorption mechanisms and final state interactions gives results that agree well with the shapes of missing energy spectra, but for some channels the predicted cross sections are too large.

The data from numerous high resolution photon scattering experiments allow an extensive survey of the lowest electric dipole excitations in the $A\simeq 130$–200 mass region. In this mass region one can find spherical as well as transitional and strongly quadrupole deformed nuclei. The measured absolute $E1\mathrm{}$ strengths are typically of the order of several milli Weisskopf units and exhibit in general a smooth variation with mass number.

We perform density dependent relativistic mean field calculations for deformed nuclei in order to examine the possibility of describing nuclear deformation properties in a parameter-free framework. The results are compared with experimental data and with results from earlier phenomenological relativistic mean field calculations using nonlinear terms in the σ field.

We study electric dipole transitions between Gamow-Teller (GT) and spin-dipole (SD) states. SD and GT excitations are calculated within the $\mathrm{H}\mathrm{a}\mathrm{r}\mathrm{t}\mathrm{r}\mathrm{e}\mathrm{e}-\mathrm{F}\mathrm{o}\mathrm{c}\mathrm{k}+\mathrm{T}\mathrm{a}\mathrm{m}\mathrm{m}-\mathrm{D}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{o}\mathrm{f}\mathrm{f}$ approximation for ${}^{48}\mathrm{Sc}$ and ${}^{90}\mathrm{Nb}.$ The electric dipole transitions are found to be rather selective, and strong $E1\mathrm{}$ transitions occur to some specific spin-dipole states. Calculated $E1\mathrm{}$ transition strengths between GT and SD states are compared with the analytic sum rules within one-particle–one-hole $\mathrm{}(1p-1h)\mathrm{}$ configuration space and within both $1p-1h$ and $2p-2h$ model space. Possible implications for charge-exchange reactions may help to understand the quenching problem of spin excitations.

The contribution of the two-nucleon emission in the longitudinal response for inclusive electron scattering reactions is studied. The model adopted to perform the calculations is based upon correlated basis function theory but it considers only first order terms in the correlation function. The proper normalization of the wave function is ensured by considering, in addition to the usually evaluated two-point diagrams, the three-point diagrams. Results for the ${}^{12}\mathrm{C}$ nucleus in the quasielastic region are presented.

In the framework of the $Q$-phonon scheme and the interacting boson model a description of the $2_1^{+}$ and $2_2^{+}$ states is obtained. The wave vectors are written as an expansion in multiple $Q$-phonon excitations of the ground state. It is shown that the convergence of this expansion is fast and the main component already provides a good approximation of the wave vector. The accuracy of such a leading-order description exceeds 90% of the wave vector. By taking into account two $Q$-phonon configurations the accuracy of the description of the $2_1^{+}$ and $2_2^{+}$ states is increased to 98%. This is true for all collective nuclei with the exception of some rotors where the first excited $K=0\mathrm{}$ band lies below or very close to the γ band and, due to band mixing, the wave vector of the $2_2^{+}$ state contains higher $Q$-phonon excitations. An application to some decay transitions is given.

The properties of superdeformed bands in ${}^{191,192}$Hg and ${}^{192,193}$Tl have been studied using the cranked Hartree-Fock-Bogoliubov method with the Lipkin-Nogami prescription, the ${\mathrm{Skm}}^{*}$ interaction, and a surface-delta, density-dependent pairing force. In particular, quasiparticle excitations involving intruder orbitals are analyzed in detail. Comparisons between data and calculations are performed for $\mathcal{J}{}^{\mathrm{}\left(2\right)\mathrm{}}$ moments, quadrupole moments, spins, transition energies, and alignments.

In order to inquire into the existence and significance of non-nucleonic degrees of freedom in the intermediate-energy regime, the production of protons and high-energy photons ${(E}_{\gamma }>30\mathrm{}$ MeV) emitted in the reaction ${}^{36}\mathrm{Ar}{+}^{27}\mathrm{Al}$ at 95 MeV/nucleon has been studied. The quantitative analysis of the $(\gamma$-$p)$ invariant-mass and relative-angle distributions shows evidences of $\Delta \mathrm{}\left(1232\right)\mathrm{}$-resonance excitation and $\overrightarrow{\Delta }N\gamma$ decay. Experimental data are in agreement with microscopic theoretical calculations.