Time evolution of hot drops of matter containing ∼230 or ∼130 particles is studied by classical molecular dynamics. Initially, the drops have uniform density and a sharp surface. The chosen initial conditions include three values of density and a range of temperatures wide enough to study the phenomena of evaporation, fragmentation, and total vaporization in a unified fashion. The average density and temperature of central matter is measured periodically to obtain trajectories of the evolution in the ρ,T plane. These trajectories indicate that the matter expands almost adiabatically until it reaches the region of adiabatic instabilities. Density inhomogeneities develop in this region, but the matter fragments only if the expansion continues to average densities of less than one-fourth the liquid density, otherwise it recondenses into a single blob. The recondensed matter and fragments have very crooked surfaces. If the temperature is high enough, the expanding matter does not enter the region of adiabatic instabilities and totally vaporizes. For initial densities of the order of equilibrium density, matter does not fragment or develop large inhomogeneities in the region enclosed by the isothermal and adiabatic spinodals. Thus it appears unlikely that fragmentation of small drops (nuclei) can be used to study the isothermal critical region of gas-liquid phase transition. A detailed tabulation of the energies and number of monomers, dimers, light, and heavy fragments emitted in each event is presented.

Angular correlations have been investigated in the ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$${(}^{16}$O,xy) reaction at 77 MeV. Using a ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ intermediate mechanism to model the interaction, attempts have been made to predict the α${+\mathrm{}}^{12}$C angular correlations at 65, 77, and 87.4 MeV. The calculations reproduce the shape of the correlations fairly well. However, the predicted angular correlation peaks too far out in angle to reproduce the experimental data. Several possible explanations for the shifting of the peaks are discussed.

We have found several new spontaneous fission (SF) activities and suggested assignments for some of them to rutherfordium (element 104) isotopes. Their half-lives and production cross sections have been measured by collecting recoils on a moving nickel or steel tape and transporting them past stationary mica track detectors at known velocities. The following tentative assignments are based on several cross bombardments and comparisons between experimental and calculated production cross sections: ${}_{}{}^{256}{}_{}{}^{}\mathrm{Rf}$(9±2 ms), ${}_{}{}^{257}{}_{}{}^{}\mathrm{Rf}$(3.8±0.8 s, 14±9% SF), ${}_{}{}^{258}{}_{}{}^{}\mathrm{Rf}$(13±3 ms), ${}_{}{}^{259}{}_{}{}^{}\mathrm{Rf}$(3.4±1.7 s, 9±3% SF), ${}_{}{}^{260}{}_{}{}^{}\mathrm{Rf}$(21±1 ms), and ${}_{}{}^{262}{}_{}{}^{}\mathrm{Rf}$(47±5 ms). Presently we are unable to assign several other new spontaneous fission activities with half-lives of ∼15 ms, ∼22 ms, ∼100 ms (Z<104), ∼1.6 s, ∼5 s, ∼5 s, ∼30 s, and ∼47 s. Contrary to other observations, we have not found any indication for an 80-ms spontaneous fission activity, earlier credited to the spontaneous fission decay of ${}_{}{}^{260}{}_{}{}^{}\mathrm{Rf}$, in reactions in which we expected to produce this isotope. Our measurements support a shift in the spontaneous fission half-life systematics at element 104, first proposed by Flerov and Oganessian et al. and later predicted by Randrup et al. and Baran et al. and attributed to the disappearance of the second hump of the double-humped fission barrier and a weakening of the 152-neutron subshell.

The isovector longitudinal and the transverse spin responses of heavy nuclei, induced by high energy proton scattering, are studied using the surface response technique. The large enhancement of the longitudinal over the transverse spin response obtained in infinite nuclear matter is found to be weakened in the surface response model. The remaining discrepancy from recent proton scattering data can essentially be explained by the isoscalar background.

Here we compare the results from the NN-πNN equation with some of the available data on pp→πd and πd→πd polarization observables. In particular, we investigate some of the uncertainties in the theoretical results due to variations in the input to the calculation. We find no major discrepancy between theory and experiment that warrants the introduction of new degrees of freedom such as dibaryons.

The transition potential for the NN→NΔ reaction is computed by considering the one-pion and one-gluon exchange mechanism in the chiral bag model. This transition potential is then used to compute ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(p,${\Delta }^{++}$)${}^6$${\mathrm{He}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}$ cross sections. The results are compared with the experimental data and with the one-pion and one-rho exchange model.

Differential cross sections for the reaction ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(p,d${\pi }^{+}$)n have been obtained at 506 MeV. The deuteron angles were 11°, 13°, 15°, and 17°, and the pions were detected at 14 angles between 24° and 96°. The data, covering the region of neutron recoil momenta 10 to 140 MeV/c, are analyzed using the plane-wave impulse approximation to extract a momentum density of the proton in the deu- teron. Systematic deviations from the plane-wave impulse approximation prediction are interpreted on the basis of a simplified calculation of the nd rescattering cross section.

The antineutron angular distribution in the reaction p¯C→n¯X was measured at 590 MeV/c. The shape of the distribution is found to be similar to that of the elementary process p¯p→n¯n, which indicates that the quasi-free process is the dominant mechanism for p¯C→n¯X. The antineutron production cross section per bound proton in the carbon nucleus is 0.14 times that for a free proton.

The process p¯p→Λ¯Λ is studied using a one-boson t-channel strangeness exchange mechanism incorporating pseudoscalar, vector, and tensor mesons. Particular attention is paid to the spin degrees of freedom in the calculation. Initial and final state interactions, including the spin-orbit interaction and absorption, are taken into account using simple phenomenological models. The calculations are performed using density matrix ideas in the helicity basis, and the most important contributing amplitudes are identified. A reasonable fit to existing data can be obtained by allowing a smooth variation of the final state parameters with laboratory momentum. The effect of each of the exchanged mesons, and of the initial- and final-state baryon-baryon interactions on the cross sections and spin observables, is discussed. It is found that the tensor meson exchange plays an essential role even near threshold, which indicates the need for a detailed understanding of the short-range spin dynamics, perhaps as provided by future quark model studies.

A phenomenological model for pion photoproduction is constructed incorporating the dynamics of pions, nucleons, and Δ’s. The importance of nonresonant background interactions for the elastic πN scattering and pion photoproduction is emphasized. The photoproduction amplitudes calculated in our model satisfy two-body unitarity, so that the requirement imposed by Watson’s theorem is automatically fulfilled. By fitting the amplitudes to data, M1 and E2 γN→Δ transition amplitudes are estimated, eliminating background contributions. The results are $A_{1/2}$(M1)=(-84±5)×${10}^{\mathrm{-}3}$ ${\mathrm{GeV}}^{\mathrm{-}1/2}$ and E2/M1=(3.7±0.4) %. Our M1 amplitude disentangled from the πN rescattering term is in good agreement with the quark model predictions. The sign and magnitude of our E2 amplitude are, however, incompatible with the existing quark models.

The half-life of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$ was determined by periodically observing the decrease in isotope abundance of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$ relative to other isotopes of plutonium with a thermal ionization mass spectrometer. A synthetic mixture of plutonium isotopes with initial values of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$${/}^{239}$Pu, ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$${/}^{240}$Pu, and ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$${/}^{242}$Pu isotope ratios close to unity was prepared. This was done with the objective of achieving high precision (better than 0.1%) in the isotope ratio measurements. The decrease in the isotope ratio was measured at intervals of 6 months over a period of about 5 yr. A value of 14.38±0.02 yr was obtained using the double ratio method which eliminates variable systematic error due to isotope fractionation. The value obtained in the present work supports the results reported earlier by the daughter growth method from this laboratory and is in good agreement with the values reported recently by other laboratories during the course of our investigations.

The extrapolated end-point of the tritium beta spectrum has been measured in a tritium-implanted Si(Li) detector for which the radiation damage has been kept small. The result is 18577±7 eV. Adding the maximum recoil energy, the ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^3{}_{}{}^{}$He atomic mass difference is taken to be 18580±7 eV.

A calculation is made of the partial half-life for the ${\beta }^{\mathrm{-}}$ decay of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ to the $5^{+}$ state of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ at 130.94±0.04 keV (an energy release of 147.1±5.0 keV). The estimated partial half-life is 760×${10}^{18}$ yr. This value is competitive with the most recent estimate of the partial half-life for the 2ν mode of double beta decay.

The search for the U(6/12) dynamical supersymmetry in the platinum isotopes is presented. The data closely examined are the energy levels and B(E2)’s for the odd- and even-mass platinums. The systematics of the data indicate that there is evidence of underlying dynamical supersymmetry.

A realistic microscopic effective nuclear Hamiltonian, $H_{\mathrm{eff}}$, is employed with the spherical finite temperature Hartree-Fock approximation to evaluate the thermodynamic properties of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. We introduce a simple method to scale $H_{\mathrm{eff}}$ to accommodate the A-dependent effects. We then adjust the Hamiltonian slightly to reproduce appropriate ground state properties within spherical Hartree-Fock theory. A range of acceptable temperatures for each model space size can then be determined. The binding energy, free energy, density distributions, entropy, neutron and proton chemical potentials and single particle energies, occupation probabilities, and other properties are evaluated for temperatures T≤7 MeV. We provide convenient parametrizations for the excitation energy, rms radius, average density, and entropy as a function of T. We find the thermal response of these nuclei to be substantially greater than that obtained with zero range phenomenological forces.

The distorted-wave Born approximation parameter $D_2$ is calculated for ${}_{}{}^6{}_{}{}^{}$Li→α+d from three-body models of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$. It is shown that the usual approximation of $D_2$ by the ratio of the D-wave to S-wave asymptotic normalization constants breaks down in this case. Because of the model dependence of $D_2$, its empirical determination should serve as a constraint on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ three-body models.

The effect of multi-quark compound states on the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ charge form factor is investigated based on the Reid soft-core potential model and the relativistic harmonic oscillator quark model. A reasonable agreement with the experimental data is obtained for the momentum transfer up to ∼1.7 GeV/c with the 2.7% six-quark compound state confined within a radius of ∼0.9 fm.

It is shown that the multiplicities of the total angular momentum projections for n-particle systems are given by the coefficients of certain Gaussian polynomials, for both bosons and fermions. These polynomials are parametrized in the same way as would be the corresponding binomial coefficients which solve the Bose-Einstein or Fermi-Dirac counting problems for the total number of allowed states. A comment on spin and statistics is included.

Proton-induced fission of ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$($E_{\mathrm{p}=200\mathrm{}}$ MeV) was investigated radiochemically in order to deduce the relative amounts of symmetric and asymmetric fission from this system. Chemical separation of K, Ni, Cu, Zn, and As was performed in these studies. The radioactive products were analyzed using Ge(Li) γ-ray spectroscopy techniques. Cumulative yields of ${}_{}{}^{42}{}_{}{}^{}\mathrm{K}$, ${}_{}{}^{65}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{66}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{67}{}_{}{}^{}\mathrm{Cu}$, ${}_{}{}^{72}{}_{}{}^{}\mathrm{Zn}$, and ${}_{}{}^{77}{}_{}{}^{}\mathrm{As}$ were measured to be 132±40, 245±120, <168, 218±50, 248±148, and 198±60 nb, respectively. If the results are cumulative yields of symmetric and asymmetric fission components, then the fission cross sections deduced from the average cumulative yields are 2.0±1.3 and 2.7±0.9μb, respectively, or a total fission cross section of 4.7±1.6μb. Alternatively, these yields can be interpreted as being due to an admixture of fission events and the high mass tail of intermediate mass fragmentation processes.

Searches have been made for the ${\beta }^{+}$/electron-capture-type double decays of ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}$, ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$, and ${}_{}{}^{96}{}_{}{}^{}\mathrm{Ru}$ and for the double ${\beta }^{+}$ decay of ${}_{}{}^{96}{}_{}{}^{}\mathrm{Ru}$. The sought-for signature of such decays was the emission of coincident back-to-back 511-keV annihilation gamma rays from the sample under study. No positive evidence of any of these decays was observed. However, from these experiments, improved lower limits on the half-lives of these nuclei against such decays have been established.