The g factor of the $2_1^{+}$ state in ${}_{}{}^{98}{}_{}{}^{}\mathrm{Sr}$ was measured by the perturbed angular correlation method at a fission product on-line separator. The result, g=0.38(7), is discussed in the framework of the proton-neutron interacting boson approximation and in relation to g${(2\mathrm{}}_1^{+}$) values for two other N=60 isotones, ${}_{}{}^{100}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{102}{}_{}{}^{}\mathrm{Mo}$.

We show that for Pauli-blocked nuclei, in the closure approximation, the summed strength for the double Gamow-Teller $0^{+}$→$0^{+}$ transitions is less than the value 6(N-Z)(N-Z+1) and that the difference can be related to sum rules for magnetic dipole transitions, which in turn can be related to the double Gamow-Teller matrix element for the transition from the $0^{+}$ initial state to its double isobaric analog state. A ‘‘wrong isospin phase sum rule’’ is found that is valid in limited cases.

The threshold energy for the ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$(p,n${)}^{10}$C reaction and the energy of the 720 keV gamma ray which follows the decay of ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$ have been measured to be 4876.91±0.10 keV and 718.353±0.011 keV, respectively. This has enabled the energy of the superallowed positron decay of ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$ to be determined to be 885.72±0.09 keV, which is a necessary step in the deduction of an accurate ft value.

A classical theory of large amplitude, adiabatic collective motion, developed and applied previously to test examples, is transcribed into the language of time-dependent Hartree-Fock theory in order to initiate the application of the new method to problems in nuclear physics. The formulation which emerges can be characterized as a generalized cranking theory, in the sense that the cranking operator cannot be chosen arbitrarily, as in the conventional formulation of this method, but is instead fully constrained by the formalism. A procedure for obtaining approximate solutions to the new equations is described and illustrated with several simplified many-body models. It is inferred that traditional cranking calculations can serve as starting points for more realistic models. This paper also includes additional discussion concerning the calculation of collective masses and the problem of local stability of collective motion, not covered in our previous work.

The response functions of nuclear matter in the region of small momentum transfer are evaluated within the framework of the random-phase approximation. The particle-hole interaction is assumed to be of the one-boson-exchange type and contains both central and tensor terms. Because of the tensor interaction six different channels, corresponding to different values of the total particle-hole spin and isospin, must be distinguished. A method that we have developed before for purely central forces is extended to the present case. This allows us to take properly into account the exchange diagrams, in the limit of small momentum transfer, even when the particle-hole interaction contains a tensor component.

The suitability of the pair condensate approach for rotational states is studied in a single j=(17/2 shell of identical nucleons interacting through a quadrupole-quadrupole Hamiltonian. The ground band and a K=2 excited band are both studied in detail. A direct comparison of the exact states with those constituting the SD and SDG subspaces is used to identify the important degrees of freedom for these levels. The range of pairs necessary for a good description is found to be highly state dependent; S and D pairs are the major constituents of the low-spin ground-band levels, while G pairs are needed for those in the γ band. Energy spectra are obtained for each truncated subspace. SDG pairs allow accurate reproduction of the binding energy and K=2 excitation energy, but still give a moment of inertia which is about 30% too small even for the lowest levels.

To the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ ground states, we apply the coupled-rearrangement-channel variational method with Gaussian-basis functions which has successfully been used in precise calculations of muonic molecular ions, Coulomb-interacting three-body systems. The trinucleon wave function is decomposed into angular-momentum-projected three-body channels as done in the Faddeev equations method, but the interaction is fully incorporated with no partial-wave decomposition. The radial part of the channel amplitudes is expanded with a sufficient number of Gaussian-tail basis functions of the Jacobi coordinates. The Gaussian ranges are taken to be geometrical progressions which run from very short ranges through large enough ones. This ab initio variational approach is found to describe accurately both the short-range correlations and the asymptotic behavior. The Argonne $V_{14}$ potential is used as an example of realistic two-nucleon interactions; for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, the Coulomb potential is included nonperturbatively. The calculation reproduces precisely the results of the Faddeev calculations for ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ for binding energy, probabilities of the S, S’, P, and D states, and the S- and D-wave asymptotic normalization constants. Convergence of the present results is seen at a much smaller number of the three-body channels than in the Faddeev calculations. This is because the interaction is truncated in the angular momentum space in the Faddeev calculations but the full interaction is taken in the present method.

A group-theoretical method for the description of the giant dipole resonance in odd-mass nuclei is described and analytical expressions for the strength splitting are derived when nuclei exhibit axially symmetric deformation, corresponding to the SU(3)⊗U(2) limit of the interacting boson-fermion model.

The ensemble average of the internal energy in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ is calculated in the finite temperature Hartree-Fock approximation and compared with the same quantity calculated exactly in the canonical ensemble. The thermal response of the different ensemble averages differs considerably for T≤2 MeV. The discrepancies can, however, easily be accounted for by the small fluctuations (1%) in the ensemble average of the number operator. A simple scheme using an approximation to the low-lying eigenspectrum of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ yields far better agreement with exact canonical ensemble results.

The accurate solutions to the low-lying eigenstates of the cranked shell model Hamiltonian are obtained by the particle-number-conserving treatment, in which a many-particle configuration truncation is adopted instead of the conventional single-particle level truncation. The variation of the seniority structures of low-lying eigenstates with rotational frequency ω is analyzed. The gap parameter of the yrast band decreases with ω very slowly, though the seniority structure has undergone a great change. It is suggested to use the seniority structure to indicate the possible pairing phase transition from a superconducting state to a normal state. The important blocking effects on the low-lying eigenstates are discussed.

The ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$(n,p) reaction at 65 MeV has been studied over a wide range of angles down to 0°. At low excitations the main strength appears to be in three concentrations of spin-dipole strength. Within certain limits Gamow-Teller ${\beta }^{+}$ strength is not evident in the spectra. Together with the earlier analysis of ${\beta }^{\mathrm{-}}$ strength in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$(p,n) these (n,p) results suggest either (1) that Gamow-Teller quenching due to Δ(isobar)-hole mixing in nuclear particle-hole excitations is relatively small (≲15%), or (2) that Δ-hole quenching is percentagewise much larger (x5) for ${\beta }^{+}$ than for ${\beta }^{\mathrm{-}}$ transitions.

Formation of ${}_{\Lambda }{}^4{}_{}{}^{}\mathrm{H}$ hypernuclei from $K^{-}$ absorption at rest on light nuclear targets was studied by measuring monochromatic ${\pi }^{-}\text{'}\mathrm{s}$ from the two-body decay, ${}_{\Lambda }{}^4{}_{}{}^{}\mathrm{H}\to {}_{}{}^4{}_{}{}^{}\mathrm{He}+{\pi }^{-}$. The formation probabilities of ${}_{\Lambda }{}^4{}_{}{}^{}\mathrm{H}$ from ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ targets were extracted to be (0.74±0.10)×${10}^{-2\mathrm{}}$, (3.0±0.4)×${10}^{-2\mathrm{}}$, (1.57±0.18)×${10}^{-2\mathrm{}}$, (1.00±0.14)×${10}^{-2\mathrm{}}$, and (0.47±0.08)×${10}^{-2\mathrm{}}$ per stopped $K^{-}$, respectively. Possible mechanisms for the production of ${}_{\Lambda }{}^4{}_{}{}^{}\mathrm{H}$ are discussed.

To explain the abundant production of ${}_{\mathrm{\Lambda }}{}^4{}_{}{}^{}\mathrm{H}$ observed in stopped-$K^{\mathrm{-}}$ absorption on light nuclei, a theoretical model is proposed, in which the basic ingredient is formation and fragmentation of a Λ compound nucleus. Estimated ${}_{\mathrm{\Lambda }}{}^4{}_{}{}^{}\mathrm{H}$ formation probabilities per stopped $K^{\mathrm{-}}$ agree with the observed values.

The nature of the first band crossing in the heavy rare-earth region is an important open spectroscopic problem. Both h(9/2 protons and i(13/2 neutrons are likely to be responsible for this phenomenon. The results of a double blocking experiment in ${}_{}{}^{178}{}_{}{}^{}\mathrm{Re}$ strongly suggest that in fact a pair of h(9/2 protons and of i(13/2 neutrons are simultaneously playing a role.

The dependence on the momentum of the nuclear mean field is studied in the framework of the self-consistent Bethe-Brueckner theory. It is pointed out that the rearrangement term, coming from the variation of the G matrix, gives a substantial contribution at the lowest momenta. The resulting single particle potential exhibits a good rate of convergence. Its momentum dependence appears to be negligible up to 2 ${\mathrm{fm}}^{\mathrm{-}1}$, in contrast with potentials used in calculations of heavy-ion collisions at intermediate energies.

We calculate the barrier penetration factor for hydrogen-like ions confined in a potential well as a function of the equilibrium separation and screening length of the medium. We show the penetration factor is extremely sensitive to these parameters, independently and in combination. The parameter values required to produce the high fusion rates reported for palladium hydride systems, however, are far from typical for these systems.

Momentum distributions in several finite nuclei are calculated in the Breuckner-Bethe-Goldstone theory. For momenta larger than 0.3 GeV/c, the distributions are dominated by two-body correlations. These affect mainly the two-nucleon s-wave channels, but also slightly modify other partial waves. By mass 12 the momentum distribution is largely saturated, and by mass 28 it is very close to that of nuclear matter. The y-scaling function suggested by West is calculated and compared to that extracted from experimental quasielastic electron scattering cross sections. The existence of a discrepancy suggests that the true scaling function is not simply related to the momentum density, even in the impulse approximation.

We present a statistical approach to the problem of multifragmentation in heavy-ion collisions. We begin with a generalized Sakur-Tetrode expression for the entropy. Through it we find expressions for the configuration weight functions. Fluctuations in the configurations are shown to be Poisson-like. Fragmentation yields are calculated by minimizing the total information subject to conservation of energy and baryon number. We work within the framework of a liquid-gas phase transition, and include a study of the effects of the nuclear surface (including a surface curvature correction), the Coulomb energy, and the internal excited states of the drop. Coulomb effects are investigated using both a simple $A^{5/3}$ dependence (as in the liquid-drop model) and a more complete expression which includes the presence of the surrounding vapor. We adopt a virial expansion for the equation of state and have found an analytic solution for the coexistence curve in infinite, uncharged matter. The case of charged, finite matter is also discussed. By identifying the clusters with the nuclei which are detected experimentally we can calculate fragment yields over a range of temperatures. We do so for a representative case and discuss the results.

We discuss mechanisms for the production of exotic hadrons in heavy-ion collisions at high energy, focusing on the doubly strange H dibaryon. In a hadron gas phase, we estimate the H formation rate, per central Si+Au collision, to be of order 0.01 for temperatures T=120–140 MeV, based on a conventional coalescence model. If the quark-gluon plasma phase is excited, we expect an enhancement relative to the rate for a hadron gas. We explore various schemes for detecting the H in the high multiplicity background characteristic of heavy-ion collisions. The proposed detection techniques include the measurement of weak decays such as H→${\Sigma }^{\mathrm{-}}$p, the search for nuclear fragments with anomalous charge/mass ratio, and diffractive dissociation processes such as Hp→${\Xi }^{\mathrm{-}}$pp. .AE

Cross sections for the elastic and inelastic scattering of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ on ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ have been calculated in a coupled-channels treatment, including the low-lying $2^{+}$ and $3^{\mathrm{-}}$ states of both projectile and target. Real, energy-independent ion-ion potentials and form factors were used, and fusion was simulated by ingoing wave boundary conditions in all channels. The agreement with the measured scattering data is qualitatively as good as obtained in previous optical-model calculations.