PROBABILITY AND TIME OF PHOTOFISSION IN THE QUASI-DEUTERON ENERGY REGION

1993 ◽  
Vol 02 (04) ◽  
pp. 827-834 ◽  
Author(s):  
G. KANIADAKIS ◽  
U. LUCIA ◽  
P. QUARATI
Keyword(s):  
Differential Equation ◽  
Numerical Analysis ◽  
Free Path ◽  
Energy Region ◽  
Mean Free Path ◽  
Point Of View ◽  
Deuteron Energy ◽  
The Mean

Using results of a previous phenomenological and numerical analysis of the photofission of Bi, Th and U in the QD energy region, we study the photofission probability as the solution of a differential equation of Clausius-Clapeyron type and derive an expression for the time of photofission. We argue about some aspects of the photofission dynamics from a thermodynamical point of view and suggest the introduction of some nuclear thermodynamical quantities. The photofission time statistically formulated on the base of the mean free path of the pn pair inside the fissioning nucleus is also examined.

scholarly journals The theory of metals. —I

1932 ◽  
Vol 138 (836) ◽  
pp. 594-606 ◽  
Keyword(s):  
Free Path ◽  
Mean Free Path ◽  
Present Theory ◽  
Point Of View ◽  
Mathematical Treatment ◽  
Constant Field ◽  
Free Electrons ◽  
The Mean ◽  
Thermal Vibrations ◽  
Good Agreement

1. The quantum theory of electrical conduction in a solid has two main problems to face, the number of “free electrons” and the “mean free path.” Of these the first is the simpler and has, to a certain extent, been solved. The evaluation of the mean free path, on the other hand, has given rise to some controversy and cannot be regarded as satisfactory. In his original paper on conduction Bloch gave a theory of the interaction of the electrons and the thermal vibrations in a metal which leaves much to be desired from the point of view of rigour, but which leads to results in good agreement with experiment. Peierls criticised this treatment and gave a new one, which, if correct, would considerably alter the theory.§ Peierls omitted most of the calculations, which are difficult, and based his treatment on physical arguments, which are by no means easy to follow, and which require justification. Recently L. Brillouin|| has given an extended mathematical treatment of the points in dispute, and obtains results which differ considerably from those of both Bloch and Peierls. None of these calculations is really satisfactory, the main objection being that the physical assumptions have not been made sufficiently precise. A method is given here which treats consistently the interaction of the electrons and the lattice, and which enables the assumptions to be clearly seen. It also has the advantage that it can be extended quite naturally to deal with the problems of the dispersion and absorption of light in metals, which will be treated in subsequent papers. In this paper the general theory will be developed, and applied to the discussion of the debatable points in the theories of Bloch and Peierls. Although the general opinion seems to be that Peierls’ criticisms are correct, the opposite view is arrived at here, and so, if the present theory is correct, the anomalous processes ” introduced by Peierls have little impor­tance for the electrical conductivity in a constant field.

The measurement of mean free path λs using a slowing down time lead spectrometer in the 1–10 eV energy region

1968 ◽  
Vol 22 (4) ◽  
pp. 261-262
Author(s):  
M.P. Navalkar ◽  
K. Chandramoleshwar ◽  
D.V.S. Ramkrishna
Keyword(s):  
Free Path ◽  
Energy Region ◽  
Mean Free Path ◽  
Slowing Down ◽  
Time Lead

scholarly journals Ballistic Heat Transport in Nanocomposite: The Role of the Shape and Interconnection of Nanoinclusions

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1982
Author(s):  
Paul Desmarchelier ◽  
Alice Carré ◽  
Konstantinos Termentzidis ◽  
Anne Tanguy
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Free Path ◽  
Mean Free Path ◽  
Strong Increase ◽  
Moderate Increase ◽  
Energy Propagation ◽  
The Mean ◽  
Dynamics Simulations

In this article, the effect on the vibrational and thermal properties of gradually interconnected nanoinclusions embedded in an amorphous silicon matrix is studied using molecular dynamics simulations. The nanoinclusion arrangement ranges from an aligned sphere array to an interconnected mesh of nanowires. Wave-packet simulations scanning different polarizations and frequencies reveal that the interconnection of the nanoinclusions at constant volume fraction induces a strong increase of the mean free path of high frequency phonons, but does not affect the energy diffusivity. The mean free path and energy diffusivity are then used to estimate the thermal conductivity, showing an enhancement of the effective thermal conductivity due to the existence of crystalline structural interconnections. This enhancement is dominated by the ballistic transport of phonons. Equilibrium molecular dynamics simulations confirm the tendency, although less markedly. This leads to the observation that coherent energy propagation with a moderate increase of the thermal conductivity is possible. These findings could be useful for energy harvesting applications, thermal management or for mechanical information processing.

Experiments on the flow of heat in liquid helium below 0.7 °K

1958 ◽  
Vol 246 (1246) ◽  
pp. 390-405 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Liquid Helium ◽  
Free Path ◽  
Empirical Relation ◽  
Mean Free Path ◽  
Series Of Experiments ◽  
The Mean ◽  
Set Up ◽  
Low Pressures ◽  
Measured Thermal Conductivity

A series of experiments has been performed to study the steady flow of heat in liquid helium in tubes of diameter 0.05 to 1.0 cm at temperatures between 0.25 and 0.7 °K. The results are interpreted in terms of the flow of a gas of phonons, in which the mean free path λ varies with temperature, and may be either greater or less than the diameter of the tube d . When λ ≫ d the flow is limited by the scattering of the phonons at the walls, and the effect of the surface has been studied, but when λ ≪ d viscous flow is set up in which the measured thermal conductivity is increased above that for wall scattering. This behaviour is very similar to that observed in the flow of gases at low pressures, and by applying kinetic theory to the problem it can be shown that the mean free path of the phonons characterizing viscosity can be expressed by the empirical relation λ = 3.8 x 10 -3 T -4.3 cm. This result is inconsistent with the temperature dependence of λ as T -9 predicted theoretically by Landau & Khalatnikov (1949).

Light scattering by phonons in the presence of a heat flow

1968 ◽  
Vol 46 (24) ◽  
pp. 2843-2845 ◽  
Author(s):  
Allan Griffin
Keyword(s):  
Light Scattering ◽  
Heat Flow ◽  
Temperature Gradient ◽  
Free Path ◽  
Mean Free Path ◽  
Photon Scattering ◽  
The Mean ◽  
Anti Stokes

If the temperature in an insulating crystal decreases in the z-direction, there are more phonons with momentum qz > 0 than with qz < 0. The resulting difference between the Stokes and anti-Stokes Brillouin intensities is proportional to the mean free path of the phonon involved and to the temperature gradient. The effect should be observable by either neutron or photon scattering.

Role of neutral-particle bombardment in dust–dust interactions in plasmas

2001 ◽  
Vol 65 (4) ◽  
pp. 257-272 ◽  
Author(s):  
Ya. K. KHODATAEV ◽  
G. E. MORFILL ◽  
V. N. TSYTOVICH
Keyword(s):  
Free Path ◽  
Particle Bombardment ◽  
Neutral Particle ◽  
Mean Free Path ◽  
Dust Particles ◽  
Neutral Particles ◽  
Additional Force ◽  
Numerical Coefficient ◽  
The Mean

It is shown that the interaction of dust with neutral plasma particles can lead to attractive forces between dust particles, both in the case where the distance between dust particles is less than the mean free path of neutral particles and in the case where it is greater. The expressions for attractive forces differs in the two limits only by a numerical coefficient. The additional force of dust interaction is found to be due to the neutrals created by recombination of charged plasma particles on the surface of dust particles. The influence of radiative dust cooling on dust–dust interaction is considered.

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