The lifetime of the 12.195 MeV level of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ was measured by the axial blocking of $\alpha$ particles from the ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}(p,{\alpha }_0)$ resonance at $E_p=632.2\mathrm{}$ keV. The result is $\tau =120\mathrm{}\pm 20$ as. The corresponding level width $\Gamma ={5.3}_{-0.8\mathrm{}}^{+0.9\mathrm{}}$ eV is in agreement with other blocking measurements but lower than that deduced from resonance reaction yields.

NUCLEAR REACTIONS ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}(p,{\alpha }_0){}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, $E=0.632\mathrm{}$ MeV; measured blocking effect and yields. ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ deduced level width. Single crystal thick Al targets. LR 115 cellulose nitrate detectors.

A measurement of the $\frac{\mathrm{}(L=2\mathrm{})\mathrm{}}{\mathrm{}(L=1\mathrm{})\mathrm{}}$ intensity ratio in the first forbidden $1^{-}$→$2^{+}$ beta branches of ${}_{}{}^{186}{}_{}{}^{}\mathrm{Re}$ and ${}_{}{}^{188}{}_{}{}^{}\mathrm{Re}$ is reported.

RADIOACTIVITY ${}_{}{}^{186,188}{}_{}{}^{}\mathrm{Re}$; measured $L_{\gamma }(\theta ,T)$. Deduced mixing ratios for $1^{-}$→$2^{+}$ beta branches.

The origin of shell effects found in the two-step ($p,d,t$) calculations, which play an important role for understanding the observed "anomalous" ($p,t$) analyzing powers, is clarified on the basis of the selection rules for transferred angular momenta.

NUCLEAR REACTIONS First- and second-order Born calculations; analyzing power $A\left(\theta \right)$; ${}_{}{}^{144}{}_{}{}^{}\mathrm{Nd}\mathrm{}(p,t)\mathrm{}{}_{}{}^{142}{}_{}{}^{}\mathrm{Nd} (\mathrm{g}.\mathrm{s}.\mathrm{},0^{+})$, $E=22.0\mathrm{}$ MeV, origin of shell effects in $A \left(\theta \right)$.

The binding energy of hyperstrange matter in the hadronic phase is calculated as a function of strangeness fraction in the mean field approximation to a relativistic field theory of matter. This is compared to a calculation of Chin and Kerman for the quark phase.

NUCLEAR STRUCTURE Nuclear matter, hyperstrange matter, quark matter.

Recent experimental data on $K^{+}$ production at 2.1 GeV/nucleon are not explained by either the cascade model or the fireball model. Here we introduce a hybrid model in which the total kaon yield is given by individual nucleon-nucleon collisions but its momentum distribution is determined by the temperature of the pion. The model is able to explain the data. The possibility of studying $K^{+}$ yield as a signature for the pionic instability in heavy-ion collisions is indicated.

NUCLEAR REACTIONS $K^{+}$ production, $K^{+}-\pi$ interaction.

The magnitudes of volume integrals per interacting nucleon pair $J_R$ calculated from a compilation of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ potentials vary between 100 and 500 MeV ${\mathrm{fm}}^3$. They are grouped in discrete branches with $J_R\mathrm{}\left(A\right)\mathrm{}$ smoothly increasing with decreasing target mass. Comparison with the results for lighter projectiles restricts the "physically meaningful" branches to those characterized by $J_R(A\ge 48)\le 270$ MeV ${\mathrm{fm}}^3$. (${}_{}{}^6{}_{}{}^{}\mathrm{Li},d$) reaction analyses yield the same fit qualities for ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ potentials of the different discrete families, but deduced spectroscopic factors jump (by factors of ∼3) when changing between successive families.

NUCLEAR REACTIONS ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ optical potential volume integrals compared with volume integrals for lighter projectiles, discussed discrete ambiguities in (${}_{}{}^6{}_{}{}^{}\mathrm{Li},d$) DWBA; target masses $A=16\mathrm{} \mathrm{to} 64$, $E\left({}_{}{}^6{}_{}{}^{}\mathrm{Li}\right)=30\mathrm{}$ MeV.

The various definitions of the quasielastic component used in the current literature are discussed and interrelated. By use of the rows-on-rows model, it is demonstrated that the direct part of a recent two-component model approximates quite well the single-collisions contribution to the one-nucleon inclusive cross section.

NUCLEAR REACTIONS Quasielastic component in high-energy nuclear collisions, knockout, single scattering, direct components of inclusive spectrum.

The multistep direct reaction method, applied earlier to fit successfully the continuum spectra of ($p,\alpha$) reactions, is shown to explain also their analyzing powers very well.

NUCLEAR REACTIONS ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}(\overrightarrow{p},\alpha )$, $E_p=65\mathrm{}$ MeV, multistep direct reaction theory analysis of the spectrum and the analyzing power.

We derive simple expressions for the low-energy behavior of direct radiative capture cross sections, particularly those important in solar nucleosynthesis, such as ${}_{}{}^3{}_{}{}^{}\mathrm{He}(\alpha ,\gamma ){}_{}{}^7{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^3{}_{}{}^{}\mathrm{H}(\alpha ,\gamma ){}_{}{}^7{}_{}{}^{}\mathrm{Li}$, and ${}_{}{}^7{}_{}{}^{}\mathrm{Be}(p,\gamma ){}_{}{}^8{}_{}{}^{}\mathrm{B}$. Our results for the ${}_{}{}^3{}_{}{}^{}\mathrm{He}(\alpha ,\gamma ){}_{}{}^7{}_{}{}^{}\mathrm{Be}$ reaction are inconsistent with a measurement by Rolfs et al.

NUCLEAR REACTIONS ${}_{}{}^3{}_{}{}^{}\mathrm{He}(\alpha ,\gamma ){}_{}{}^7{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^3{}_{}{}^{}\mathrm{H}(\alpha ,\gamma ){}_{}{}^7{}_{}{}^{}\mathrm{Li}$, $E<\mathrm{}300\mathrm{}$ keV, ${}_{}{}^7{}_{}{}^{}\mathrm{Be}(p,\gamma ){}_{}{}^8{}_{}{}^{}\mathrm{B}$, $E<\mathrm{}100\mathrm{}$ keV, extrapolated $S$.

A new and model independent method is proposed as a means of extracting the neutron-neutron scattering parameters. This is done by exploiting the analyticity of reaction cross sections in the internal kinetic energy of a two particle subsystem in the final state.

NUCLEAR REACTIONS Neutron-neutron final state interaction peak. Analyticity structure of cross sections. Empirical continuation.

It is suggested that nuclear quasimolecular spectra are dominated by dipole rather than quadrupole degrees of freedom. An algebraic approach to these dipole modes in terms of the group U(4) is proposed. One of the dynamical symmetries of the corresponding algebraic structure, O(4), is discussed and shown to yield spectra of molecular rotation-vibration type.

NUCLEAR REACTIONS Quasimolecular spectra, algebraic approach, O(4) symmetry.

All the available data concerning barrier region resonances in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ system have been examined within the framework of the molecular symmetry model suggested by Iachello. The model accounts very well for the energies and spins of the observed resonances in terms of vibrational and rotational excitations of a well-defined diatomic molecule.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ barrier resonances $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=3.1\mathrm{}-13$ MeV; application of a molecular symmetry model.

The weak neutral axial current gives rise to coherent elastic scattering of neutrinos by nuclei with static spin-isospin order or pion condensation. The cross section is comparable to that for normal nuclei at much lower momentum transfer. This allows one to perform the experiment at values of the momentum transfer high enough for the recoil nucleus to be detectable and the contribution to the cross section from the vector current to be negligible.

NUCLEAR REACTIONS Intermediate energy cross section for elastic neutrino scattering by nuclei, momentum transfer ≫ inverse nuclear radius, sensitivity of the cross section to static spin-isospin order.

Several models of light fragment emission are confronted with data from electron and proton induced reactions. The data appear to favor a mechanism, called the snowball model here, in which there is a single collision of the projectile and a few collisions of the secondary nucleons which then form the observed fragment. The parameter of the model is determined by fitting new isotopically separated inclusive differential cross section data.

NUCLEAR REACTIONS Statistical, knockout, and coalescence models, light fragment emission, electron and proton induced reactions.

Using the analytic hadron-nucleus scattering amplitudes of Amado, Dedonder, and Lenz, one can show how to account for Coulomb effects approximately by a simple alteration of any medium energy amplitude that excludes such effects. The method is based on an asymptotic (large momentum transfer) approximation and so works best where numerical methods experience the greatest technical difficulties.

NUCLEAR REACTIONS Approximating Coulomb distortion in intermediate energy hadron-nucleus scattering.

The limitations imposed by Porter-Thomas fluctuations in the study of primary $\gamma$ rays following neutron capture have been partly overcome by obtaining individual $\gamma$-ray spectra from 48 resonances in the ${}_{}{}^{173}{}_{}{}^{}\mathrm{Yb}(n,\gamma )$ reaction and summing them after appropriate normalizations. The resulting average radiation widths (and hence the $\gamma$-ray strength function) are in good agreement with the Axel-Brink predictions based on a giant dipole resonance model.

NUCLEAR REACTIONS ${}_{}{}^{173}{}_{}{}^{}\mathrm{Yb}(n,\gamma )$, $E_n=0.01\mathrm{}-0.52$ keV, measured $E_{\gamma }$, $I_{\gamma }$. ${}_{}{}^{174}{}_{}{}^{}\mathrm{Yb}$ deduced levels, $\gamma$-ray strength function. Enriched target. Ge(Li) detector. Comparison with giant dipole resonance model predictions.