A recent experiment by the TRIPLE Collaboration on the helicity dependence of the transmission of epithermal neutrons by ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ has yielded a surprise: The data do not display the expected randomness in sign. We develop a systematic theory of parity violation in this reaction and investigate the mechanism which may cause the observed asymmetry.

The fusion cross section is obtained in the framework of the ‘‘shadow’’ model. The parameters, which appear in the analytical expression of the fusion cross section, are determined by fitting the experimental values of the fusion cross section. The cross section factor 〈σv〉 is obtained by using this fusion cross section and by assuming that the distribution of the relative velocity between two different sets of particles is described by a Maxwell-Boltzmann distribution. The values of 〈σv〉 at different temperatures are determined by performing numerical integrations. At energies at which the experimental data are available the obtained cross section factor values coincide with those reported in the literature; at very low energies experimental data are not available and our approach is able to give the values of the cross section factor.

A ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ beam with an energy of E/A=70 MeV has been used to produce new isotopes near the proton drip line. The Michigan State University National Superconducting Cyclotron Laboratory A1200 fragment separator was used to detect the new isotopes ${}_{}{}^{78}{}_{}{}^{}\mathrm{Y}$, ${}_{}{}^{82}{}_{}{}^{}\mathrm{Nb}$, ${}_{}{}^{85}{}_{}{}^{}\mathrm{Mo}$, ${}_{}{}^{86}{}_{}{}^{}\mathrm{Tc}$, and ${}_{}{}^{89,90}{}_{}{}^{}\mathrm{Ru}$.

We have searched for the ingrowth of ${}_{}{}^{244}{}_{}{}^{}\mathrm{Cm}$ in a 1.45-g sample of ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$. We isolated a curium fraction after an ingrowth period of 1.03 yr; during this time the ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$ sample produced ≤0.24 alpha disintegrations per day of ${}_{}{}^{244}{}_{}{}^{}\mathrm{Cm}$ (95% C.L.), corresponding to a half-life for the double beta decay of ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$ of ≥1.1×${10}^{18}$ yr.

The reaction ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$${(}^{13}$C,3n) at bombarding energies close to the Coulomb barrier has been reinvestigated in order to study low-spin states in ${}_{}{}^{218}{}_{}{}^{}\mathrm{Ra}$ and to determine the position of the $1^{\mathrm{-}}$ and the $3^{\mathrm{-}}$ states. Although several new levels could be identified, none of them is compatible with the deexciting of the $1^{\mathrm{-}}$ state. This result opposes a previous work, which assigns the $1^{\mathrm{-}}$ state to an ${\mathit{E}}_{\mathit{x}}$=713 keV level.

Incomplete-fusion excitation functions are calculated for the systems ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${+}^{40}$Ca and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$${+}^{200}$Hg taking into account the temperature dependence of the free interaction energy and a realistic dynamical treatment of preequilibrium emission of nucleons before the fusion process. The inhibition to fusion of the hot rotating composite due to opening of fission channels is also investigated.

In this Brief Report, electric quadrupole corrections to the two-neutron removal cross section measured in heavy ion collisions are estimated for ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$ targets. The quadrupole process is assumed to proceed primarily through excitation of the giant isovector quadrupole resonance, which then decays by neutron emission. For ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$, the contribution from E2 radiation is found to be small, while for ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ we find the quadrupole contribution resolves the discrepancy between experiment and the simple predictions of the Weissacker-Williams virtual photon method.

We investigate the longitudinal and transverse momentum distributions of charged fragments originating from reactions with radioactive, neutron-rich beams. It is shown that the width of the narrow peak of the longitudinal momentum distribution is insensitive to the details of the collision and the size of the target nucleus. In contrast, the width of the peripheral region from which transversely moving particles originate is significantly narrowed via absorption of the outgoing neutrons. This diffractively broadens the width of their transverse momentum distribution, in a manner which depends on details of the collision, and so makes the transverse distribution less reliable than the longitudinal one for measuring the size of the original neutron halo.

The angular momentum, angular velocity, Kelvin circulation, and vortex velocity vectors of a quantum Riemann rotor are proven to be either (1) aligned with a principal axis or (2) lie in a principal plane of the inertia ellipsoid. In the second case, the ratios of the components of the Kelvin circulation to the corresponding components of the angular momentum, and the ratios of the components of the angular velocity to those of the vortex velocity, are analytic functions of the axes lengths.

Excited states in the doubly odd nucleus ${}_{}{}^{80}{}_{}{}^{}\mathrm{Rb}$ have mainly been studied via the ${}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}$${(}^{19}$F,α3n) reaction at 72 MeV beam energy utilizing the NORDBALL detector system. The level scheme has been extended up to a (${15}^{+}$) state at 4446 keV excitation energy. In the low-spin region seven new isomers with lifetimes in the nanosecond region have been found. In addition, a $6^{+}$ isomer with a half-life of the order of μs has been identified at an excitation energy of 494.4 keV. For the level sequence built on this isomer positive parity is suggested and the states are ascribed to the intruder two-quasiparticle configuration (π${\mathit{g}}_{9/2}$⊗ν${\mathit{g}}_{9/2}$) and collective excitations.

Limits on double beta decays of ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$ to excited states in ${}_{}{}^{100}{}_{}{}^{}\mathrm{Ru}$ were made via exclusive measurements for the first time by looking for two individual β rays in coincidence with γ decays from the excited states. Stringent lower limits on the half-lives for the neutrinoless (0νββ) and two-neutrino (2νββ) processes to the $2_1^{+}$ and $0_1^{+}$ excited states were deduced.

Six superdeformed bands have been found in the nucleus ${}_{}{}^{192}{}_{}{}^{}\mathrm{Tl}$. For two of the bands, the dynamic moment of inertia ${\mathit{J}}^{\mathrm{}\left(2\right)\mathrm{}}$ is found to be constant with the rotational frequency ħω. This result can be understood in terms of Pauli blocking of quasiparticle alignments in intruder orbitals, and represents strong experimental evidence that the alignment of these intruders is responsible for the smooth rise in ${\mathit{J}}^{\mathrm{}\left(2\right)\mathrm{}}$ seen in other superdeformed nuclei of this mass region.

Ground and isomeric states of a nucleus have been resolved for the first time by mass spectrometry. Measurements on ${}_{}{}^{78}{}_{}{}^{}\mathrm{Rb}_{}^{\mathit{m},}{}_{}{}^{}$g and ${}_{}{}^{84}{}_{}{}^{}\mathrm{Rb}_{}^{\mathit{m},}{}_{}{}^{}$g were performed using a tandem Penning trap mass spectrometer on-line with the isotope separator ISOLDE/CERN. The effects of ion-ion interaction were investigated for two ion species differing in mass and stored simultaneously in the trap.

Multifragmentation is observed with an improved Boltzmann-Uehling-Uhlenbeck model for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{51}$V and ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$${+}^{92}$Mo collisions. For ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ induced reactions, however, a single residue is observed up to energy E/A≊200 MeV. By investigating the dependence on the masses of the projectile and target and on the equation of state, we demonstrate that the dynamics of compression and expansion, rather than the thermal excitation energy, plays the dominant role in causing the observed multifragmentation.

It has recently been shown that the twist-two valence quark distributions calculated in the MIT bag model are in reasonable agreement with world data. Furthermore, several authors have constructed mean-field theories which reproduce the saturation properties of nuclear matter in terms of a mean-field theory of nonoverlapping bags, self-consistently bound by scalar and vector meson exchange. By using a local density approximation we combine these developments to microscopically investigate the structure functions of finite nuclei. Not only do we obtain a semiquantitative description of the data (the so-called European Muon Collaboration effect) but we also show that the conventional treatment based on nucleon binding is quantitatively unreliable.

We consider two separate schemes for eliminating the explicit summation over states in the intermediate nucleus in double-beta decay. The first, known as the operator expansion method, has recently been applied in several calculations; we show in a variety of simple models that the method fails and isolate its weaknesses. We then describe an efficient technique for generating Green’s function matrix elements, based on the Lanczos algorithm, and apply it to a full fp-shell calculation in ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$. The method efficiently generates an exact (to within machine accuracy) result while the operator expansion method is again inaccurate.

Measurements of the analyzing power ${\mathit{A}}_{\mathit{y}}$(θ) for neutron-proton scattering have been performed at 7.6, 12.0, 14.1, 16.0, and 18.5 MeV. The experimental setup is described as are the finite-geometry corrections applied to the data. One of these corrections, due to the presence of carbon in the scintillators used for neutron detection, is discussed in detail. The ${\mathit{A}}_{\mathit{y}}$(θ) data are compared to the predictions of the Paris and Bonn nucleon-nucleon potentials and the predictions of two phase-shift analyses, one of which incorporates charge-independence breaking effects in the ${}_{}{}^3{}_{}{}^{}$P waves.

Three-body nuclear reactions with Coulomb interaction are treated using the formalism of Alt, Sandhas, and Ziegelmann when two of the three particles are charged. Aspects of the numerical calculation are discussed and its difficulties are pointed out. Calculations are presented by considering the total energy of the system under breakup threshold and increasing values of the target atomic number.