12,045 research outputs found
Comparison of Canonical and Grand Canonical Models for selected multifragmentation data
Calculations for a set of nuclear multifragmentation data are made using a
Canonical and a Grand Canonical Model. The physics assumptions are identical
but the Canonical Model has an exact number of particles, whereas, the Grand
Canonical Model has a varying number of particles, hence, is less exact.
Interesting differences are found.Comment: 12 pages, Revtex, and 3 postscript figure
On the Molecular Conductivity of Dyestuffs in Solution and the Influence of Foreign Substance on the Same
The paper describes the results of the measurements of the molecular conductivities of dyestuffs in solution. It has been found that in most of the eases the molecular conductivities
of dyestuffs in solution do not have linear relations with square root of concentration. The departure of the conductivity curve from the perfect straight line has been explained as due
to the formation of ionic micelles. The influence of foreign molecule or ions on the conductivity of the fluorescent dyestuffs in solution has been investigated as well
A study of the phase transition in the usual statistical model for nuclear multifragmentation
We use a simplified model which is based on the same physics as inherent in
most statistical models for nuclear multifragmentation. The simplified model
allows exact calculations for thermodynamic properties of systems of large
number of particles. This enables us to study a phase transition in the model.
A first order phase transition can be tracked down. There are significant
differences between this phase transition and some other well-known cases
Isospin fluctuations in spinodal decomposition
We study the isospin dynamics in fragment formation within the framework of
an analytical model based on the spinodal decomposition scenario. We calculate
the probability to obtain fragments with given charge and neutron number,
focussing on the derivation of the width of the isotopic distributions. Within
our approach this is determined by the dispersion of N/Z among the leading
unstable modes, due to the competition between Coulomb and symmetry energy
effects, and by isovector-like fluctuations present in the matter that
undergoes the spinodal decomposition. Hence the widths exhibit a clear
dependence on the properties of the Equation of State. By comparing two systems
with different values of the charge asymmetry we find that the isotopic
distributions reproduce an isoscaling relationship.Comment: 18 RevTex4 pages, 6 eps figure
Incorporating Radial Flow in the Lattice Gas Model for Nuclear Disassembly
We consider extensions of the lattice gas model to incorporate radial flow.
Experimental data are used to set the magnitude of radial flow. This flow is
then included in the Lattice Gas Model in a microcanonical formalism. For
magnitudes of flow seen in experiments, the main effect of the flow on
observables is a shift along the axis.Comment: Version accepted for publication in Phys. Rev. C, Rapid Communicatio
Distinguishing impurity concentrations in GaAs and AlGaAs, using very shallow undoped heterostructures
We demonstrate a method of making a very shallow, gateable, undoped
2-dimensional electron gas. We have developed a method of making very low
resistivity contacts to these structures and systematically studied the
evolution of the mobility as a function of the depth of the 2DEG (from 300nm to
30nm). We demonstrate a way of extracting quantitative information about the
background impurity concentration in GaAs and AlGaAs, the interface roughness
and the charge in the surface states from the data. This information is very
useful from the perspective of molecular beam epitaxy (MBE) growth. It is
difficult to fabricate such shallow high-mobility 2DEGs using modulation doping
due to the need to have a large enough spacer layer to reduce scattering and
switching noise from remote ionsied dopants.Comment: 4 pages, 5 eps figure
Nuclear Chemical and Mechanical Instability and the Liquid-Gas Phase Transition in Nuclei
The thermodynamic properties of nuclei are studied in a mean field model
using a Skryme interaction. Properties of two component systems are
investigated over the complete range of proton fraction from a system of pure
neutrons to a system of only protons. Besides volume, symmetry, and Coulomb
effects we also include momentum or velocity dependent forces. Applications of
the results developed are then given which include nuclear mechanical and
chemical instability and an associated liquid/gas phase transition in two
component systems. The velocity dependence leads to further changes in the
coexistence curve and nuclear mechanical and chemical instability curves.Comment: 21 pages, 9 figures, Results are changed due to error in progra
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