123108693
Connection of Kukulin's nucleon-nucleon deep potential with realistic repulsive core interactions
The on-shell equivalence of the deep quantum-chromodynamically motivated realistic nucleon-nucleon interaction recently proposed by Kukulin et al. with more conventional repulsive-core forces is investigated by eliminating its unphysical deeply bound states, while preserving its scattering properties and the binding energy of the deuteron. The resulting interaction, which is built both in the singlet and triplet channels, displays ar−2 singular repulsive core followed by a shallow attraction of intermediate range, in good semiquantitative agreement with existing realistic nucleon-nucleon interactions.
123123854
Evidence for alpha-particle clustering in the Ti44 nucleus
The ..cap alpha..-particle cluster structure of /sup 44/Ti, which is of considerable interest for investigation of the persistence of ..cap alpha.. clustering in the region of the sd-shell closure, is studied within the frame of a local-potential approach. It is shown that the model leads to specific predictions if continuity with existing unique ..cap alpha..+ /sup 40/Ca optical potentials is insisted upon; in particular, the existence of an as yet experimentally unknown ..cap alpha..-cluster negative-parity band, starting just above the ..cap alpha..+ /sup 40/Ca threshold, is strongly suggested.
42706318
Alpha-cluster spectroscopy in 40Ca and in the sd-shell closure region.
The low-energy {sup 36}Ar({alpha},{alpha}) elastic scattering data of Gaul {ital et} {ital al}. are analyzed within the frame of the optical model, using energy-independent Woods-Saxon squared or model-independent geometries for the real part of the potential. The optical-model scattering amplitude is decomposed into its barrier and internal wave components to understand the rapid and complicated evolution of the angular distributions with incident energy. The properties of the low-energy bound and quasibound states supported by this potential are compared with those of the states of the deformed 4p-4h rotational band in {sup 40}Ca, built on the {ital J}{sup {pi}}=0{sup +}, {ital E}{sub {ital x}}=3.35 MeV state. The possibility of extending this local potential model approach to neighboring nuclei near the {ital sd}-shell closure is discussed. A negative-parity band of states with appreciable {alpha}-cluster character, starting around the {alpha}-particle threshold, is expected to be systematically present in this mass region.
46627030
A potential deduced from low energy 16O( alpha, alpha ) elastic scattering.
The properties of the {alpha}+{sup 16}O interaction in the vicinity of the Coulomb barrier are investigated by constructing (real, energy-independent) potentials which reproduce---when resonant nonpotential contributions are added to the potential background---all available {sup 16}O({alpha},{alpha}) elastic scattering angular distributions and excitation functions between 3.5 and 9 MeV incident energies. These low energy potentials, which are constructed for angular momenta ranging from 0 to 5, are in line with the global potential extracted from the analysis of the higher energy data (20{le}{ital E}{sub {alpha}}{le}150 MeV), but a slight angular momentum dependence, and an increase of the barrier height of about 1 MeV, are found necessary to reproduce the low energy data; this effect is qualitatively similar to that predicted by calculations taking into account antisymmetrization or dispersion relation effects. These potentials reproduce the properties of the first three members of the {sup 20}Ne {ital K}{sup {pi}}=0{sub 4}{sup +} ``higher nodal`` rotational band, which dominate the scattering in the investigated energy range, and of the {ital J}{sup {pi}}=5{sup {minus}} member of the {ital K}{sup {pi}}=0{sup {minus}} ``inversion doublet`` band. By taking into account the energy dependence of the interaction at lower energy, these potentials also give a nice account of the propertiesmore » of the {ital J}{sup {pi}}=1{sup {minus}} and 3{sup {minus}} members of the same band, and are found to be compatible with the properties of the first three members of the {sup 20}Ne ground state band.« less
119969931
Optical-model Description of Alpha+o-16 Elastic-scattering and Alpha-cluster Structure in Ne-20
O16(,) elastic scattering angular distributions have been measured for incident energies 39.3, 49.5, and 69.5 MeV. These data, and previous measurements at 32.2, 104, and 146 MeV, have been subjected to a global optical model analysis. The deduced global potential has two energy-dependent parameters which are found to vary smoothly with energy and it is uniquely determined by the data. Backward angular distributions measured between 40 and 54 MeV are also presented and shown to be nicely reproduced by the model. The sensitivity of the cross sections to the various regions of the real potential has been investigated as a function of energy using the notch test technique. The low energy behavior of the differential cross sections can be understood in terms of the semiclassical decomposition of Brink and Takigawa. A natural extrapolation of the global potential below 30 MeV is shown to reproduce the wide bump observed in the experimental excitation functions around 20 MeV. This bump is shown to be due to an l=8 shape resonance and is interpreted as the J=8+ member of the K=04+ rotational band of Ne20, in contradiction with the current attribution. Other bound and quasibound states supported by the potential are discussed in the light of orthogonality condition model-type arguments and shown to be consistent with the well-known K=01+ and 0- bands, and with the first three states of the K=04+ band of Ne20. NUCLEAR REACTIONS O16(,), measured (), E=39.3, 49.5, 69.5 MeV; global optical model analysis, E=32-146 MeV; semiclassical decomposition of the scattering amplitude; investigation of the compatibility of the potential description with existing low energy data and comparison with cluster models. © 1983 The American Physical Society.
26446865
Negative-parity inversion doublet alpha -cluster band in 18O.
123629832
Intense Coherent Submillimeter Radiation in Electron Storage Rings
Energetic electron bunches in storage rings produce pulsed bursts of incoherent synchrotron radiation. It is pointed out that they should also produce a roughly comparable power output of coherent radio-frequency radiation. Thus electron storage rings, in addition to their intended purpose and their secondary use as intense sources of x rays, might additionally serve as pulsar simulators, producing a similar spectrum of coherent emission, the properties and modification of which could be studied in the laboratory. A spontaneous bunching of electrons (artificially bunched here) might be evidenced as ''superbunching.''
123416974
Theory of pulsar magnetospheres
There is a wide range of fundamental physical problems directly related to how pulsars function. Some of these are independent of the specific pulsar mechanism. Others relate directly to the physics of the pulsar and already shed some light on the properties of matter at high density (\ensuremath{\sim}${10}^{15}$ g/cc) and in strong magnetic fields (\ensuremath{\sim}${10}^{12}$ G). Pulsars are assumed to be rotating neutron stars surrounded by strong magnetic fields and energetic particles. It is somewhere within this "magnetosphere" that the pulsar action is expected to take place. Currently there has been considerable difficulty in formulating an entirely self-consistent theory of the magnetospheric behavior and there may be rapid revisions in the near future, which is all the more surprising since many of the issues involve "elementary" problems in electromagnetism. One interesting discovery is that charge-separated plasmas apparently can support stable static discontinuities.
119697750
Gravitationally induced electric fields in conductors.
An estimate for the gravitationally induced electric field is presented that is based on a statistical model for the electrons in a metal in which their long-range electrostatic interaction with a differentially compressed lattice of positive ions is taken into account. The field is in the upward direction and is estimated to be of the order of magnitude $E\ensuremath{\approx}\frac{\mathrm{Mg}}{e}$, where $M$ is the atomic mass, $e$ is the electronic charge, and $g$ is the acceleration due to gravity. For copper, $E\ensuremath{\approx}{10}^{\ensuremath{-}7}$ V/m. An earlier estimate by Schiff and Barnhill gives a field in the downward direction equal to $\frac{\mathrm{mg}}{e}$, where $m$ is the mass of the electron. The difference between our result and theirs is due to different treatments of the effect of lattice compressibility.
121467224
PARITY NONCONSERVATION IN NUCLEI
BS>The influence of the known weak interactions on the parity of nuclear states is discussed. Derivation of a parity nonconserving interaction rests on the assumption of a current-current hypothesis for the weak interactions. Consequently, observation of parity impurity effects would be an important confirmation of this hypothesis. A simple approximate method of treating the nuclear parity impurity is developed and applied in an effort to find experimental situations favorable to observation of effects due to such impurity. Parity-forbidden alpha decay from excited states of light nuclei and certain electromagnetic transitions in the heavy nuclei appear to be promising. Special attention was paid to the internal conversion electrons from the 123kev transition nn Lu/sup 173/ whose polarization is estimated to be about 0.4%. An effect on polarized neutrons analogous to optical rotation is also discussed. (auth)