Charged pion exchange, resulting in an n${\Delta }^{++}$ state, contributes positively to the weak scattering asymmetry in longitudinally polarized p→p scattering at medium energy. This pion-exchange contribution combined with the traditional ρ and ω ‘‘elastic’’ contributions moves the total theoretical prediction into better agreement with the 800-MeV experimental data point. The pion-exchange contribution has both inelastic and elastic scattering components and is sizable even below the pion production threshold. Strong distortions enhance the magnitude of the effect.

The results of the Nijmegen soft-core potential model are presented for the low-energy YN interactions. The YN version of the model is obtained by a straightforward extension of the NN model through the application of SU(3). The potentials are due to the dominant parts of the π, η, η’, ρ, ω, φ, δ, ɛ, and $S^{\mathrm{*}}$ Regge trajectories. This gives the traditional one-boson-exchange potentials. In addition to these, the J=0 contributions from the tensor f,f’,$A_2$ and Pomeron trajectories are included in the potentials. The latter give potentials of the Gaussian type. Also the form factors from Regge poles are Gaussian, which guarantees that the potentials have a soft behavior near the origin. The multichannel Schrödinger equation is solved in configuration space for the (partially) nonlocal potentials. We work on the particle basis and include the Coulomb interaction exactly.

The meson-baryon coupling constants are calculated via SU(3), using the coupling constants of the NN analysis as input. Charge symmetry breaking in the Λp and Λn channels is included. An excellent description is achieved of the available low-energy data per degree of freedom (${\chi }^2$≊0.58 for 35 YN data). In particular, we were able to fit the inelastic capture ratio at rest perfectly. We have $r_R$=0.471, where experimentally the average value is $r_R$=0.468±0.010. The obtained values for the adjustable mixing angles and F/(F+D) ratios agree very well with the literature. We find ${\alpha }_{\mathrm{PV}=0.355\mathrm{}}$ and ${\alpha }_V^m$=0.275. For the scalar-meson mixing angle we obtain ${\theta }_s$=40.895°, which lies between the ideal mixing angles for the scalar $q^2$q¯ ${}_{}{}^2{}_{}{}^{}$ and qq¯ states. In the Λp system we find a cusp at the ${\Sigma }^{+}$n threshold, but there is on the second Riemann sheet no pole in the vicinity causing this cusp. The predictions of the total cross sections up to the pion production threshold are given and compared to the experimental data.

Nuclear magnetic resonance on oriented nuclei has been observed for ${}_{}{}^{193}{}_{}{}^{}\mathrm{Os}$ (${\mathit{I}}^{\mathrm{\pi }}$=(3/$2^{\mathrm{-}}$;$T_{1/2}$=30.0 h) as dilute impurity in Fe, the zero-field hyperfine splitting frequency being 410.2(2) MHz. With the hyperfine field $B_{\mathrm{HF}}$(OsFe)=-1106.3(3) kG and taking into account the uncertainties introduced by the unknown hyperfine anomaly and the resonance displacement caused by an unresolved quadrupole interaction, the g factor and magnetic moment of ${}_{}{}^{193}{}_{}{}^{}\mathrm{Os}$ are deduced to be g=+0.4864(11) and μ=+0.7297(16) ${\mu }_N$. .AE

The β/γ and delayed proton decays of mass separated A=141 isotopes with Z=63–66 were investigated with an on-line mass separator. Branching ratios have been redetermined for the total β decay of the 2.7(3) s, ${(11/2\mathrm{}}^{\mathrm{-}}$ isomer ${}_{}{}^{141}{}_{}{}^{}\mathrm{Eu}_{}^{\mathrm{m}}{}_{}{}^{}$ at 96.5 keV (${13}_{\mathrm{-}2}^{+4\mathrm{}}$%), and for the direct β feeding of the 1.58 keV ${(3/2\mathrm{}}^{+}$ level of ${}_{}{}^{141}{}_{}{}^{}\mathrm{Sm}$ in the decay of 40-s ${}_{}{}^{141}{}_{}{}^{}\mathrm{Eu}_{}^{\mathrm{g}}{}_{}{}^{}$ [73(5)%]. Detailed decay schemes have been constructed for the decays of the ${(11/2\mathrm{}}^{\mathrm{-}}$ isomer ${}_{}{}^{141}{}_{}{}^{}\mathrm{Gd}_{}^{\mathrm{m}}{}_{}{}^{}$ [11(2)% isomeric transition] and the ${(1/2\mathrm{}}^{+}$ ground state, ${}_{}{}^{141}{}_{}{}^{}\mathrm{Gd}_{}^{\mathrm{g}}{}_{}{}^{}$. Half-lives of 24.5(5) s and 14(4) s, respectively, have been determined for these isomers. A delayed proton branch of 0.03(1)% was identified in the decay of ${}_{}{}^{141}{}_{}{}^{}\mathrm{Gd}_{}^{\mathrm{g}}{}_{}{}^{}$. A detailed decay scheme was also constructed for 3.5(2)-s ${}_{}{}^{141}{}_{}{}^{}\mathrm{Tb}$ and a $J^{\pi }$${=(5/2\mathrm{}}^{\mathrm{-}}$ was assigned to its ground state, at variance with the systematics of heavier, odd-mass Tb isotopes. All γ-ray assignments to the various isotopes are based on xγ and γγ coincidences and on half-life measurements. A 0.9(2)-s half-life for ${}_{}{}^{141}{}_{}{}^{}\mathrm{Dy}$ was determined from its delayed proton decay. All spin assignments proposed in this paper are discussed in terms of Nilsson level diagrams and nuclear shapes.

Nuclear core-polarization diagrams for the neutrinoless ββ decay of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ are calculated using a M-3Y effective G-matrix interaction. Comparing with the respective closed core calculations, the main effect of these diagrams is to decrease the limit on light neutrino mass or increase the limit on heavy neutrino mass by about 10%.

We describe a hybrid method of calculating exciton state and level densities which combines the calculation of energy-dependent spin moments with a combinatorial calculation of the energy dependence of the total density of states. We show, in an example, that the spin distribution is well approximated by a distribution constructed from the moments.

A method is presented for random-phase-approximation calculations of nuclear response in the continuum. It utilizes the Lanczos method for solving the basic inhomogeneous coupled-channel integral equation. The method can provide information on both the direct and statistical decay components. We illustrate the usefulness of the method by applying it to calculate the $2^{+}$ strength functions for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ in the giant quadupole resonance region. It is shown that the calculations reproduce the observed peak positions and widths very well.

A recently proposed matrix formulation of the WKB quantization rule and the usual WKB quantization rule are tested in the case of short-range potentials in one dimension which are nonsingular at the origin. Such potentials simulate optical potentials in nuclear physics. We compare the results for the bound states of these two semiclassical quantization rules with the exact solution of the Schrödinger equation and find that usually both of these approximations yield good results. In particular, the newly proposed matrix formulation of the WKB quantization rule produces results either comparable to or better than results obtained with the usual WKB quantization rule for the low-lying states which are very interesting from a physical point of view as they simulate the ground and a couple of excited states of the nuclear optical potential.

The idea of ‘‘universality’’ of an average nuclear field introduced earlier has been applied and tested in the calculations of B(E2;$0_1^{+}$→$2_1^{+}$) values and nucleon separation energies for nuclei in the Z≥52,A≥120 region. Good description is obtained using a single ‘‘universal’’ choice of 12 constants defining the deformed Woods-Saxon nuclear average field.

The magnetic form factors of ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ are calculated with the Monte Carlo method from variational ground-state wave functions obtained for the Argonne and Urbana two- and three-nucleon interactions. The electromagnetic current operator contains one- and two-body terms that are constructed so as to satisfy the continuity equation with the two-nucleon potential in the Hamiltonian. The results obtained with the Argonne two-nucleon interaction are in overall agreement with the empirical values. It appears that the remaining theoretical uncertainty, in the calculation of these form factors from a given interaction model, is dominated by that in the electromagnetic form factors of the nucleon. It is found that the isovector magnetic form factors are rather sensitive to the details of the isospin-dependent tensor force, and they are much better reproduced with the Argonne than the Urbana potential. The isoscalar magnetic form factors appear to be sensitive to the spin-orbit interactions, and are better reproduced with the Urbana potential. The Argonne potential has a stronger ${\tau }_1$⋅${\tau }_2$ tensor force, while the Urbana one has a shorter-range spin-orbit interaction.

The levels of ${}_{}{}^{60}{}_{}{}^{}$,61Zn and ${}_{}{}^{59}{}_{}{}^{}$,60Cu have been investigated using γ-γ coincidence spectroscopy in the reactions ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$(α,n${)}^{61}$Zn at 13 MeV, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$(α,nγ${)}^{61}$Zn at 11.5, 15, and 20 MeV, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${(}^6$Li,p2nγ${)}^{61}$Zn at 30 MeV, ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$${(}^{10}$B,p2nγ${)}^{61}$Zn at 45 MeV, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${(}^{24}$Mg,2pnγ${)}^{61}$Zn at 65 and 80 MeV, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${(}^3$He,nγ${)}^{60}$Zn at 8 and 12 MeV, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${(}^{23}$Na,p2nγ${)}^{60}$Zn at 70 MeV, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${(}^3$He,pnγ${)}^{59}$Cu at 12 MeV, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$(α,pnγ${)}^{60}$Cu at 20 MeV, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${(}^{23}$Na,2pnγ${)}^{60}$Cu at 70 MeV. In the helium-induced reactions, spectra were gated with neutron coincidences. New levels have been found in all the nuclides studied, and a number of new spin assignments were made on the basis of n-γ angular correlations. The results are compared with earlier γ-ray and particle studies, and with preexisting shell-model predictions.

We present a version of the random-phase approximation for the description of nuclear excitations which is a consistent extension of the QHD1 mean-field theory of the ground states of doubly magic nuclei. This approach includes correlations induced by the isoscalar σ and ω mesons of QHD1. Our method employs a nonspectral single particle propagator in such a way that we avoid any basis truncation and automatically include the escape widths implied by the theory. Our calculations yield exactly conserved random-phase approximation transition currents as well as correct treatment of spuriosity for $1^{\mathrm{-}}$T=0 excitations. Because of the flexibility of our numerical method, we can treat discrete excitations, giant resonances, and the continuum response in general—including quasielastic scattering—in a unified way. We compare our results with experimental (e,e’) form factors for various discrete excitations in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ as well as with the quasielastic Coulomb response functions for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. Agreement with transition charge densities is typically quite good and in some cases superior to comparable nonrelativistic random-phase approximation calculations. Transition current densities are less well described. The question of sum rules in the relativistic random-phase approximation is also addressed.

All the data now available for the ground rotational bands of actinide even-even nuclei and of rare-earth even-even nuclei (with bandcrossing angular momentum $I_c$≥16) are analyzed with the four-parameter I(I+1) expansion. The parameters obtained by the least-squares fitting definitely deviate from the relations derived from the Harris two-parameter ${\omega }^2$ expansion, but are closer to the relations deduced from the closed two-parameter expression by Wu and Zeng.

The boson expansion technique, extensively used in the past to describe anharmonic effects in spherical nuclei, is used to derive a boson formalism in a deformed basis (Nilsson model). The new formalism is then used to describe anharmonic gamma vibrations in ${}_{}{}^{168}{}_{}{}^{}\mathrm{Er}$. The Hamiltonian adopted for practical calculations includes monopole and quadrupole pairing, and quadrupole particle-hole interactions. Some effects due to the coupling of the collective-noncollective modes and a three-body interaction are also taken into account in a perturbative fashion.

A simple bosonic model that has two different phases, one corresponding to a condensate of bosons, a situation that resembles spherical nuclei, and a second one of a condensate of pairs of bosons that corresponds to nuclei where the ground state is a condensate of alphalike clusters, is solved in several different approximate treatments and exactly. Some differences due to the finite number of bosons from the known results for large boson systems are obtained.

The shell-model fermion problem for systems of four protons and four neutrons in single-j shells is transformed into a boson problem using the generalized Dyson boson mapping. Exact boson calculations are performed. The spectrum of physical and nonphysical boson states and the effect of truncation in the boson space are studied. The necessity of transformation from the Dyson boson description to the seniority boson description is demonstrated within the truncated space.

A description of small amplitude oscillations around a stationary state in nuclear matter is formulated in the context of the relativistic Vlasov equation. We obtain a set of stationary linear modes of excitation satisfying orthogonality and completeness relations. For longitudinal modes it is explicitly shown that the system, which is made up of relativistic particles in interaction with an external scalar meson field, behaves like a system of fermions very weakly coupled to the scalar meson field, even if the coupling constant is large.

We discuss the construction of ideal space seniority images of single fermion operators which proceeds via the generalized Dyson mapping and a subsequent similarity transformation. Particular attention is paid to the implications of a consistent treatment of single-particle and collective degrees of freedom. The results are compared with expressions for the mapped single fermion operators previously obtained, respectively, within the Otsuka-Arima-Iachello framework and by using the prescriptions of nuclear field theory. We point out certain inconsistencies in existing constructions of interacting-boson-fermion model operators in general and the interacting-boson-fermion model quadrupole operator in particular.

A search for the production of bound tetraneutrons has been carried out with a time projection chamber using the reaction ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(${\pi }^{\mathrm{-}}$,${\pi }^{+}$${)}^4$n at &=80 MeV and at &<130°. No evidence for tetraneutron formation was found, and a 90% confidence level upper limit for the production cross section of dσ/dΩ≤13 nb ${\mathrm{sr}}^{\mathrm{-}1}$ was obtained.

Two recent photon scattering experiments agree within 1% on a rather large peak cross section for the giant-dipole resonance of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$, but disagree in the width by 14%. We show that photo- neutron data strongly favor the larger width and, therefore, the larger enhancement factor of ${\kappa }_{\mathrm{GDR}=0.46\mathrm{}\pm 0.05}$. .AE