89 research outputs found
Coherent photon bremsstrahlung and dynamics of heavy-ion collisions: comparison of different models
Differential spectra of coherent photon bremsstrahlung in relativistic heavy
ion collisions are calculated within various schematic models of the
projectile-target stopping. Two versions of the degradation length model, based
on a phenomenological deceleration law, are considered. The simple shock wave
model is studied analytically. The predictions of these models agree in the
soft photon limit, where the spectrum is determined only by the final velocity
distribution of charged particles. The results of these models in the case of
central Au+Au collisions at various bombarding energies are compared with the
predictions of the microscopic transport model UrQMD. It is shown that at the
AGS energy the coherent photon bremsstrahlung exceeds the photon yield from
-decays at photon energies \omega\loo 50 MeV.Comment: 23 pages RevTeX, 9 eps Figure
Non-linear excitations in Ising-type magnetic chain systems I: Mossbauer relaxation studies of antiferromagnets in zero and applied field
Quantum Matter and Optic
Novel A15 phase in barium-doped fullerite
A new stable compound Ba3C60 is reported in the Ba-C60 phase diagram. Rietveld refinement of x-ray powder diffraction data shows that this compound has the A15 structure with a lattice constant of 11.34. The Pm3Ìn space group implies a perfect alternating orientational order for the C60 molecules, not previously observed in doped fullerite structures. The relative stability of the A15 phase over the fully intercalated fcc structure can be explained by a simple model involving the Madelung energy differences, orientation dependence of the C60-cation interaction energy, and distortion-induced relaxational energy gains
Field-dependent Mossbauer relaxation study of domain walls in the quasi 1-d antiferromagnet RbFeCl3.2H2O
Quantum Matter and Optic
Exact soliton solution and inelastic two-soliton collision in spin chain driven by a time-dependent magnetic field
We investigate dynamics of exact N-soliton trains in spin chain driven by a
time-dependent magnetic field by means of an inverse scattering transformation.
The one-soliton solution indicates obviously the spin precession around the
magnetic field and periodic shape-variation induced by the time varying field
as well. In terms of the general soliton solutions N-soliton interaction and
particularly various two-soliton collisions are analyzed. The inelastic
collision by which we mean the soliton shape change before and after collision
appears generally due to the time varying field. We, moreover, show that
complete inelastic collisions can be achieved by adjusting spectrum and field
parameters. This may lead a potential technique of shape control of soliton.Comment: 5 pages, 5 figure
Pseudotenfold symmetry in pentane-solvated C60 and C70
Crystals of C60 or C70 cocrystallized with n-pentane grow as elongated, ten-sided columns. X-ray diffraction shows ordering of C60 or C70 molecules along the column and a remarkable tenfold symmetry normal to the column. The ratio of the x-ray-diffraction vectors of the two lowest-order diffraction spots is nearly equal to the âgolden ratio,â Ï. Despite these similarities with decagonal, quasicrystalline order, the diffraction indicates crystalline order with a twinned unit cell
Measurements of 12C(→Îł,pp) photon asymmetries for EÎł= 200â450 MeV
The 12C (→γ ,pp) reaction has been studied in the photon energy range 200-450 MeV at the Mainz microtron MAMI-C, where linearly polarised photons were energy-tagged using the Glasgow-Mainz Tagged Photon Spectrometer and protons were detected in the Crystal Ball detector. The photon asymmetry ÎŁ has been measured over a wider EÎł range than previous measurements. The strongest asymmetries were found at low missing energies where direct emission of nucleon pairs is expected. Cuts on the difference in azimuthal angles of the two ejected protons increased the magnitude of the observed asymmetries. At low missing energies the ÎŁ data exhibit a strong angular dependence, similar to deuteron photodisintegration
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