Gamow-Teller (GT) strength has been extracted from cross sections for the reaction ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$(n,p${)\mathrm{}}^{54}$Mn at 0°, 2.5°, 5°, 8°, and 12°, and for an incident energy of 298 MeV. This determination of the ${\beta }^{+}$ GT strength $S_{+}$ allows for the first time a full test of the Ikeda sum rule. These data also show that the best available shell-model calculations overestimate this strength by a factor of 2. This result is significant in models of supernovae since electron capture in (fp)-shell nuclei, which is proportional to $S_{+}$, depletes the relativistic electron gas in precollapse stars.

We study the quantum relativistic Coulomb-excitation process including recoil effects in the plane-wave Born approximation. It is shown that there exists an interplay between quantum and relativistic recoil effects in certain kinematical regions which cannot be accounted for in the conventional theories. This specific feature is shown to modify the angular distribution of Coulomb-induced fission fragmentation in an essential manner. In contrast with usual treatments we find that our results compare favorably with recent data.

The nucleus ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$, with sharp ridges in the γ-γ energy correlation matrix, stands out from three neighboring nuclei which exhibit less pronounced structures. The ridges include the observed discrete superdeformed band, but must be composed mainly of unresolved superdeformed bands, which decay predominantly to less deformed states. A simple decay model is proposed.

First evidence of the nucleus ${}_{}{}^{22}{}_{}{}^{}\mathrm{Si}$ (${\mathrm{T}}_{\mathrm{z}}$=-3) is observed by fragmentation of 85-MeV/nucleon ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ projectiles from the Grand Accélérateur National d’Ions Lourdes.

Supersymmetric quantum mechanis is applied to the determination of a shallow potential which is phase equivalent to a deep potential, and whose bound spectrum is identical except for the ground state which is suppressed. With this method, the nonphysical bound states encountered in the spectrum of microscopically founded potentials can be eliminated. The resulting shallow potentials present for small r values an ${\mathrm{r}}^{\mathrm{-}2}$ singularity in accord with a generalized Levinson theorem.

Triple coincidences between intermediate-mass fragments and angle-correlated binary fission events were measured in the at E/A=35 MeV. It was found that fragments emitted at backward angles appear to be associated with reactions in which nearly all ofthe projectile momentum is carried away by the heavy reaction residue and the intermediate-mass fragment. In contrast, fragments emitted at forward angles are accompanied by 20%–30% missing momentum.

Let α be the relative norm of a symmetry-breaking term in the Hamiltonian of a many-particle system, and Λ the energy-dependent transition parameter which charcterizes the quantum chaos via spectral and strength fluctuations. Combining a compact theory for Λ/${\mathrm{\alpha }}^2$ with fluctuation theories by which Λ can be deduced from (neutron-resonance) data gives, for the time-reversal-noninvariant nucleon-nucleon interaction, α≤(1–2)×${10}^{\mathrm{-}3}$, which would improve with better small-strength data in nuclei with dense spectra. Diffusion equations involving Λ as the ‘‘time’’ variable are also discussed.

Spin-flip probabilities have been measured for inelastic proton scattering from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at 319 MeV at angles between 3° and 12° and excitation energies up to about 40 MeV. These data can be directly related to the relative [(spin transfer)/(no spin transfer)] nuclear response via one model-dependent variable. Nuclear spin excitations appear relatively suppressed at low excitation energies but surprisingly enhanced at the highest excitation energies at intermediate angles. Many features of the data can be explained with a slab nuclear response with random-phase-approximation correlations.

We have measured the energy and angular dependence of charged-pion production, with associated multiplicity selection, in La + La collisions at 138, 183, and 246 MeV/nucleon. The pions are produced mainly in collisions with a large number of participants. The general behavior of the spectra is consistent with results at higher energies, but the yield of subthreshold pions depends much more strongly upon the target and projectile mass. The pion spectra at 246 MeV/nucleon exhibit a strong charge dependence.

Constraints on right-handed currents are set by the precise comparison of the longitudinal polarizations $P_{\mathrm{F}}$ and $P_{\mathrm{GT}}$ in Fermi and Gamow-Teller ${\beta }^{+}$ decay. Measurements with a new fourfold Bhabha polarimeter gave $P_{\mathrm{F}/P_{\mathrm{GT}=1.003\mathrm{}\pm 0.004}}$ with use of the matching isotopes ${}_{}{}^{26\mathrm{m}}{}_{}{}^{}\mathrm{Al}$ and ${}_{}{}^{30}{}_{}{}^{}\mathrm{P}$. This ratio translates directly into a bound on the product of the mixing angle ζ and mass-squared ratio δ of the left- and right-handed W bosons given by -0.49<δζ×${10}^3$<1.2 at 90% confidence.

We present a mechanism for the separation of strangeness from antistrangeness in the deconfinement transition. For a net strangeness of zero in the total system, the population of s quarks is greatly enriched in the quark-gluon plasma, while the s¯ quarks drift into the hadronic phase. This separation could result in ‘‘strangelet’’ formation, i.e., metastable blobs of strange-quark matter, which could serve as a unique signature for quark-gluon plasma formation in heavy-ion collisions.

Isotopically resolved yields of intermediate-mass fragments from ${}_{}{}^{12}{}_{}{}^{}\mathrm{-}$ and ${}_{}{}^{18}{}_{}{}^{}\mathrm{induced}$ reactions on ${}_{}{}^{58}{}_{}{}^{}$,64Ni, ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Ag}$, and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ at E/A=84 MeV were measured. The systematic variation of the yield ratios with projectile and target shows that these fragments are produced by a mechanism that involves the whole target nucleus. It is demonstrated that, within a statistical interpretation, the isotope-yield ratios are a measure of the entropy and determine a relation between temperature and density at breakup.

The deuteron magnetic form factor B($Q^2$) has been measured at momentum transfers $Q^2$=1.21, 1.49, 1.61, 1.74, 1.98, 2.23, 2.48, 2.53, and 2.77 (GeV/c${)}^2$ at the Stanford Linear Accelerator Center by detection of electrons backscattered at 180° in coincidence with recoiling deuterons at 0°. The data for B($Q^2$) are found to decrease rapidly from $Q^2$=1.2 to 2 (GeV/c${)}^2$, then rise to a secondary maximum around $Q^2$=2.5 (GeV/c${)}^2$, in qualitative agreement with impulse-approximation calculations.

A quasielastic (e,e’p) experiment has been performed on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ for both backward- (transverse) and forward-angle (longitudinal) electron kinematics. Cross sections for knockout of protons from two different orbits (1s and 1p) have been measured simultaneously. The densities probed by the (e,e’p) reaction differ by a factor of 4 between these orbits. In both cases the backward/forward cross-section ratio deviates by the same amount from the impulse approximation.

Cascade-model calculations are extended to study the pion energy spectra in high-energy heavy-ion collisions of heavy systems. It is found that pion reabsorption (π+N→Δ) is essential in explaining the difference between the energy slopes for pions and protons. This pion-reabsorption effect becomes more and more important as the mass number increases and reproduces even the observed falloff of the energy slopes (temperatures) for pions in the collisions of heavier nuclei. We show also the average pion multiplicities with mass number.

Synthetic small-angle excitation functions and angular distributions are calculated for the reaction ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$,${\alpha }_0$)${}^{28}$Si by use of a compound-nucleus decay model which includes angular momentum conservation. Fluctuations in the synthesized cross sections are shown to exhibit all the general characteristics of measured ${\alpha }_0$ cross sections, including features usually attributed to resonances.

On-line resonance-ionization mass spectrometry has been applied to determine the isotope shift and hyperfine structure of ${}_{}{}^{185\mathrm{-}189}{}_{}{}^{}\mathrm{Au}$ and ${}_{}{}^{189\mathrm{m}}{}_{}{}^{}\mathrm{Au}$ in the 6s ${}^2$$S_{1/2}$→6p ${}^{2p}$${}_{1/2}$ (λ=268 nm) transition. The Au atoms were obtained as daughters of mass-separated Hg isotopes produced at the ISOLDE facility at CERN ionized by a three-color, two-step resonant photoionization process, detected and mass-selected by time of flight. A drastic change of the nuclear charge radius was observed between ${}_{}{}^{187}{}_{}{}^{}\mathrm{Au}$ and ${}_{}{}^{186}{}_{}{}^{}\mathrm{Au}$, which is interpreted as an onset of strong deformation of β≊0.25 in ${}_{}{}^{186}{}_{}{}^{}\mathrm{Au}$ and ${}_{}{}^{185}{}_{}{}^{}\mathrm{Au}$.

The proton-induced fission cross section for ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ targets has been measured for ${\mathrm{E}}_{\mathrm{p}}$=1–4 MeV for the first time. Compared with the measurements at higher energies, the present results indicate a pronounced change in the slope of the excitation function below 4 MeV such that standard optical-model estimates fall far short of the observed cross sections. No plausible explanation in terms of fission of either the target or the compound nucleus can be found.

We have measured the single and correlated magnetic-substate population parameters for the $2^{+}$ and $2^{+}$-$2^{+}$ excitations in ${}_{}{}^{24}{}_{}{}^{}$Mg${+\mathrm{}}^{24}$Mg in the region of two strong resonances seen in inelastic scattering. We interpret our data in terms of an isolated resonance decaying through one preferred l value in both the $2^{+}$ and $2^{+}$-$2^{+}$ channels. Our data suggest a spin assignment of $J^{\pi }$${=36\mathrm{}}^{+}$ for the resonance at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}=45.70\mathrm{}}$ MeV, and a value of l=34 for the grazing angular momentum for both the single and mutual inelastic-scattering channels.

The astonishing smoothness of the superdeformed rotational spectrum in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$, from I=22 to I=60, is used as a basis for inferring a liquid-to-solid transition as the centrifugal force drives the nuclear shape into a closed-shell configuration.