The relationship between observed intermediate mass fragment and total charged particle multiplicities has been measured for ${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$ + ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ collisions at energies between E/A=35 and 400 MeV. Fragment multiplicities are greatest for central or near-central collisions. For these collisions, fragment production increases up to E/A≊100 MeV, and then decreases at higher energies.

Angular distributions and total cross sections for the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(${\mathrm{\pi }}^{+}$,pp${)}^2$H reaction have been measured with small relative uncertainties at incident energies of ${\mathit{T}}_{\mathrm{\pi }}^{+}$=64, 87, 114, 162, 217, 278, and 327 MeV. The results strongly support the quasideuteron absorption model for pion absorption on two nucleons, which is found to contribute only ≊50% to the total absorption cross section near the Δ resonance. All essential reaction channels of pion absorption near the Δ resonance on heavier nuclei seem to be present in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, but not in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. Any nuclear-density-related increase of pion absorption in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ relative to ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ is <50% and no binding energy effect is found.

Ten transitions linking the superdeformed band to the normal deformed states have been identified in ${}_{}{}^{133}{}_{}{}^{}\mathrm{Nd}$. These transitions drain the full band intensity into the different band structures established at lower spin. The major part of the decay out of the superdeformed band is understood in terms of mixing of levels which involve orbitals differing by two major oscillator quantum numbers.

We present the first results of a calculation of kinematically complete differential cross sections for the proton-induced deuteron breakup reaction, obtained by using a three-body formalism based on momentum space integral equations which correctly takes into account the Coulomb repulsion between the two protons. Comparison with experimental data is made.

A novel effect of the neutron halo formation is presented for the direct radiative neutron capture where a p-wave neutron is captured into an s orbit with neutron halo by emitting an E1 γ ray. As an example, an enormous enhancement is demonstrated for the cross section of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(n,γ${)}^{13}$C(1/$2^{+}$) at low energy in excellent agreement with a recent experiment. The S factor of the final state is evaluated. The inverse process, i.e., photo disintegration is discussed for an example of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$. A sharp but nonresonant peak near the threshold is obtained as a result of the neutron halo in its anomalous ground state.

The off-shell expansion of the s-wave πN amplitude suggests that the s-wave interaction of space-like pions with the nuclear medium is appreciably repulsive. This has consequences for the experiments aimed at the exploration of the spin longitudinal response or of the pion excess in nuclei. It may offer in particular an explanation for the (p,n) puzzle where the attraction from the pion exchange force has failed to appear.

This Rapid Communication discusses possible reasons for the discrepancy between the results of the Garching and Dubna determinations of the mean square intrinsic charge radius of the neutron related to the inner structure of the neutron. It is shown that the most probable reason for the discrepancy between the values for bismuth is the differences in accounting for the influence of negative energy resonances on the (ne)-scattering length value measured in the experiments. The Dubna result seems to be more reliable for the present.

Experimental data on the angular momentum dependence of parity splitting of yrast bands in different nuclei are analyzed using a one-dimensional model of octupole motion with axial symmetry. A two parameter formula, based on a solution of the Schrödinger equation with a double-minimum potential, predicts that the parity splitting exponentially decreases with I(I+1) and gives a good fit to these data. Moreover, it relates the observed parity splitting directly to the internal barrier height of the potential.

Longitudinal, transverse, and longitudinal-transverse structure functions for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(e,e’p) reaction have been determined. Measurements of the cross sections were made in-plane in nearly quasielastic kinematics spanning momentum transfers between 200 and 670 MeV/c and recoil momenta between 0 and 150 MeV/c. In addition, cross sections at momentum transfers above 800 MeV/c were measured at backward scattering angles in aligned kinematics where the response is predominantly transverse. We compared our data with both relativistic and nonrelativistic models. Our results are not consistently in agreement with any of the calculations based on these models. The disagreement between our data and these calculations ranges from 0% to 30%; on average it is about 10%. Notable discrepancies arise in describing relativistic effects for the longitudinal-transverse structure function, at a momentum transfer of 400 MeV/c as well as for the transverse structure function at momentum transfer above 800 MeV/c.

The interaction between a nucleon and a Δ isobar is studied. The nucleon-Δ potential is derived from a nonrelativistic quark model. It is compared with a corresponding one based on meson exchange. The quark-model potential is strongly repulsive at small relative distances. The effects of the potential on elastic and inelastic nucleon-nucleon and pion-deuteron scattering are calculated. Some observables show sensitivity with respect to the chosen nucleon-Δ potential.

We present new effective internucleon forces responsible for the microscopic α-cluster model. We introduce the two- and three-body operators with finite ranges, which play an essential role in accounting for the bulk properties of nuclei in a broad range of masses including nuclear matter. The proposed forces are suitable for analyzing the elastic α-α scattering.

We evaluate the two pion exchange contribution to the nucleon-nucleon potential in configuration space using a minimal chiral model containing only pions and nucleons. The scalar-isoscalar component of the interaction is relatively small, due to cancellations between large terms, and fails to reproduce the intermediate range attraction in the central channel. We show that these results do not depend on how chiral symmetry is implemented.

Approximate analytical formulas for the self-consistent renormalization of P,T-odd and P-odd weak nuclear potentials by the residual nucleon-nucleon strong interaction are derived. The contact spin-flip nucleon-nucleon interaction reduces the constant of the P,T-odd potential 1.5 times for the proton and 1.8 times for the neutron. Renormalization of the P-odd potential is caused by the velocity dependent spin-flip component of the strong interaction. In the standard variant of π+ρ exchange, the conventional strength value leads to anomalous enhancement of the P-odd potential. Moreover, the π-meson exchange contribution seems to be large enough to generate an instability (pole) in the nuclear response to a weak potential.

A complete potential model for nucleon-nucleon bremsstrahlung is used to test t matrices of recent NN potentials. ppγ and npγ cross sections and spin observables are calculated using the Paris, Bonn-B, and inversion potentials to the most recent phase shift analyses and Bonn-B phase shifts. We confront our results with older noncoplanar ppγ data from Harvard and most recent but inclusive data from Saclay and the Indiana University Cyclotron Facility. We obtain a good agreement between experiment and theory for all potentials. Nonlocality effects of potentials, supposedly discerned by bremsstrahlung, are small in comparison to data errors and differences between the potentials themselves.

The ${}_{}{}^{154}{}_{}{}^{}\mathrm{Gd}$ nucleus was studied by γ-ray spectroscopy following the (α,2n) reaction at an energy of 26 MeV. We identified the double-phonon K=$4^{+}$ γγ vibrational band in this nucleus at 1645.8 keV. Also, we present the systematics of possible K=$4^{+}$ double phonon vibrational bands in the deformed rare-earth region of nuclei.

It has been known for many years that the first excited state of ${}_{}{}^{229}{}_{}{}^{}\mathrm{Th}$ lies close to the ground state. Originally this energy was given as <0.1 keV; later, the authors reported a value of -1±4 eV. In an attempt to improve the value for this level energy, we have remeasured the energies of a number of γ rays from ${}_{}{}^{223}{}_{}{}^{}\mathrm{U}$ whose positions in the ${}_{}{}^{229}{}_{}{}^{}\mathrm{Th}$ level scheme can be used to establish it. Compared with our earlier study, we have considered more γ rays in ${}_{}{}^{229}{}_{}{}^{}\mathrm{Th}$, used more well-measured energy calibration and reference lines, used more detectors, used detectors with better low-energy resolution, more closely matched the counting rates in the γ-ray peaks whose relative energy is measured, and specifically considered certain systematic errors. More than 111 γ-ray spectra have been measured. From this large set of measurements we have deduced a value of 3.5±1.0 eV for the energy of this level.

Electron-capture delayed fission ECDF was studied in the new isotope ${}_{}{}^{238}{}_{}{}^{}\mathrm{Bk}$ produced via the ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$(75-MeV α, 7n${)}^{238}$Bk reaction. The half-life of the fission activity was measured to be 144±5 seconds. The mass-yield distribution is predominantly asymmetric and the most probable preneutron emission total kinetic energy of fission is 179±7 MeV. The ECDF mode in ${}_{}{}^{238}{}_{}{}^{}\mathrm{Bk}$ was verified by an x-ray-fission coincidence experiment which indicated that the ${}_{}{}^{238}{}_{}{}^{}\mathrm{Cm}$ fission lifetime is between about ${10}^{\mathrm{-}15}$ and ${10}^{\mathrm{-}9}$ seconds. The isotope was assigned to ${}_{}{}^{238}{}_{}{}^{}\mathrm{Bk}$ through chemical separation and observation of the known 2.4-h ${}_{}{}^{238}{}_{}{}^{}\mathrm{Cm}$ daughter activity. No alpha branch was observed in the decay of ${}_{}{}^{238}{}_{}{}^{}\mathrm{Bk}$. The production cross section for ${}_{}{}^{238}{}_{}{}^{}\mathrm{Bk}$ is 150±20 nb and the delayed fission probability is (4.8±2)×${10}^{\mathrm{-}4}$.

The β-delayed α spectrum of ${}_{}{}^{17}{}_{}{}^{}\mathrm{N}$ has been measured using a molecular ${}_{}{}^{17}{}_{}{}^{}\mathrm{NO}_{}^{+}{}_{}{}^{}$ beam from the TRIUMF isotope separator. Thin surface barrier detector pairs were used to count the α particles in coincidence with ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ recoil nuclei. The resulting spectrum has been fitted with a K-matrix parametrization. The β-delayed α decay of states at 7.99 and 8.20 MeV in the ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ daughter has been observed. A total βα-branching ratio of (2.5±0.4)×${10}^{\mathrm{-}5}$ has been determined for this decay mode of ${}_{}{}^{17}{}_{}{}^{}\mathrm{N}$.

The level structure of ${}_{}{}^{212}{}_{}{}^{}\mathrm{Bi}$ has been studied by observing the alpha decay of ${}_{}{}^{216}{}_{}{}^{}\mathrm{At}$ which is in secular equilibrium with ${}_{}{}^{220}{}_{}{}^{}\mathrm{Fr}$ and ${}_{}{}^{224}{}_{}{}^{}\mathrm{Ac}$. Eight states are observed and tentatively assigned to the configuration π${\mathit{h}}_{9/2}$ν(${\mathit{g}}_{9/2}$${)}^3$ and three to the configuration π${\mathit{h}}_{9/2}$ν(${\mathit{g}}_{9/2}$${)}^2$${\mathit{i}}_{11/2}$. These two lowest configurations in ${}_{}{}^{212}{}_{}{}^{}\mathrm{Bi}$ are compared with the corresponding configurations in ${}_{}{}^{210}{}_{}{}^{}\mathrm{Bi}$ and the calculations of Warburton.

Lifetime measurements of levels in ${}_{}{}^{121}{}_{}{}^{}\mathrm{I}$, populated via the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$${+}^{114}$Cd reaction at 51 MeV, have been undertaken using the recoil-distance (plunger) method. Transitions from the noncollective oblate (γ=+60°) state associated with band termination and from the collective oblate (γ=-60°) band head to prolate states have been observed to be significantly hindered; mean lifetimes of τ=(379±32) ps for the 39/$2^{\mathrm{-}}$ state at 5433 keV and τ=(83±17) ps for the 11/$2^{\mathrm{-}}$ state at 1327 keV, respectively, have been measured. In addition, a mean lifetime of τ=(273±10) ps was determined for the 11/$2^{\mathrm{-}}$ state at 811 keV.