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The mean free time for a molecule in a fluid is the average time between collisions. The mean free path of the molecule is the product of the average speed and the mean free time. [1] These concepts are used in the kinetic theory of gases to compute transport coefficients such as the viscosity. [2] In a gas the mean free path may be much larger ...
In physics, mean free path is the average distance over which a moving particle (such as an atom, a molecule, or a photon) travels before substantially changing its direction or energy (or, in a specific context, other properties), typically as a result of one or more successive collisions with other particles.
The amount of deflection depends on the speed of the carrier and its proximity to the ion. The more heavily a material is doped, the higher the probability that a carrier will collide with an ion in a given time, and the smaller the mean free time between collisions, and the smaller the mobility. When determining the strength of these ...
mean free path, the average distance between two subsequent collisions of the electron (ion) with plasma components: , =, ¯,, where , ¯ is an average velocity of the electron (ion) and , is the electron or ion collision rate.
where is the current density, is the external electric field, is the electronic density (number of electrons/volume), is the mean free time and is the electron electric charge. Other quantities that remain the same under the free electron model as under Drude's are the AC susceptibility, the plasma frequency , the magnetoresistance , and the ...
The inelastic mean free path of electrons can roughly be described by a universal curve that is the same for all materials. [1] [3] The knowledge of the IMFP is indispensable for several electron spectroscopy and microscopy measurements. [4]
The electron mean free path can become long compared to the gap between the electrodes. In this case, the electrons might gain large amounts of energy, but have fewer ionizing collisions. A greater voltage is therefore required to assure ionization of enough gas molecules to start an avalanche.
Here t is the time, p is the average momentum per electron and q, n, m, and τ are respectively the electron charge, number density, mass, and mean free time between ionic collisions. The latter expression is particularly important because it explains in semi-quantitative terms why Ohm's law , one of the most ubiquitous relationships in all of ...