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Prompt $\ensuremath{\gamma}$-ray cascades in neutron-rich nuclei around doubly magic ${}^{132}\mathrm{Sn}$ have been studied at Eurogam II using a ${}^{248}\mathrm{Cm}$ fission source. Yrast states to above 5.5 MeV in the two- and three-proton $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}82$ isotones ${}^{134}\mathrm{Te}$ and ${}^{135}\mathrm{I}$ are reported. They are interpreted in terms of valence proton and particle-hole core excitations with the help of shell model calculations employing empirical nucleon-nucleon interactions from both ${}^{132}\mathrm{Sn}$ and ${}^{208}\mathrm{Pb}$ regions. A serious inconsistency in the accepted masses of $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}82$ isotones near ${}^{132}\mathrm{Sn}$ is discovered but not resolved.

The Eurogam-2 array has been used to study {gamma} rays emitted following the spontaneous fission of a {sup 248}Cm source. Analysis of Doppler-broadened line shapes corresponding to decays from excited rotational states in neutron-rich Sr, Zr, and Mo fission fragments has enabled the first measurements of state lifetimes in these nuclei at around {ital I}=10. The results are consistent with a predicted rotation-induced change in the triaxiality of the yrast states of the Mo isotopes that contrasts with the more stable behavior observed in the Zr and Sr nuclei. {copyright} {ital 1996 The American Physical Society.}

The neutron-rich ${}^{106}$Mo nucleus has been studied by prompt \ensuremath{\gamma}-ray spectroscopy following the spontaneous fission of ${}^{248}$Cm. The characteristics of the rotational band built on a state at 1435 keV identifies the band head as the best candidate for a harmonic double-phonon ${K}^{\ensuremath{\pi}}{\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4}^{+}$ \ensuremath{\gamma}-vibrational state observed so far.

We present data on collective flow of neutrons in collisons of [sup 197]Au + [sup 197]Au at 400 MeV/nucleon. The azimuthal distribution about the beam axis is investigated with respect to the reaction plane as determined from light charged particles. The squeezeout'' of neutrons, perpendicular to the reaction plane, is observed for the first time. Quantitative agreement to a high level of accuracy is found between the behavior of neutrons and hydrogen ions.

The nuclear response of a medium-mass nucleus ([sup 136]Xe) to electromagnetic excitation in a near-relativistic heavy-ion collision was investigated in the reaction[sup 136]Xe(0.7[ital A] GeV)+Pb. From an exclusive measurement of the neutron decay of the excited [sup 136]Xe projectiles, strong excitations of giant resonances and, in particular, of the double isovector giant dipole resonance were identified. A resonance energy of 28.3[plus minus]0.7 MeV, a width of 6.3[plus minus]1.6 MeV, and a total cross section of 215[plus minus]50 mb were found for the double giant dipole resonance.

Differential cross sections for electromagnetic fission of 238U projectiles (500 MeV/u) in C, Sn, and Pb targets are measured and analyzed in terms of single- and multiphonon giant resonance excitations as doorway states to fission. A novel experimental method exploits the linear relationship between neutron multiplicity and the primary 238U excitation energy. Multiphonon states contribute up to 20% of the cross section; a component at high excitation energies is indicated that may arise from three-phonon dipole and two-phonon GDR x GQRiv giant resonance excitations.

The dipole response of stable and unstable neutron-rich oxygen nuclei of masses A = 17 to A = 22 has been investigated experimentally utilizing electromagnetic excitation in heavy-ion collisions at beam energies about 600 MeV/nucleon. A kinematically complete measurement of the neutron decay channel in inelastic scattering of the secondary beam projectiles from a Pb target was performed. Differential electromagnetic excitation cross sections d sigma/dE were derived up to 30 MeV excitation energy. In contrast to stable nuclei, the deduced dipole strength distribution appears to be strongly fragmented and systematically exhibits a considerable fraction of low-lying strength.