Local thermodynamic equilibrium in a laser-induced plasma channel formed by interaction of femtosecond laser radiation with argon

In this paper, we estimate the possibility of applying local thermodynamic equilibrium conditions for a laser-induced plasma channel formed by femtosecond laser radiation in an argon medium at different pressures. The presence of a local thermodynamic equilibrium was determined on the basis of the time of heat exchange of electrons with argon atoms. The Saha equation is used to estimate the concentration of free electrons, the temperature of the laser-induced plasma channel, and its conductivity. A necessary condition for using this ratio was the presence of a state of local thermodynamic equilibrium in the plasma under study.

Ionization equilibrium in a highly imperfect smoke plasma

The ionization equilibrium in a heterogeneous strongly nonideal smoky plasmas containing condensed particles and an easily ionized addition of cesium atoms in the gas phase is considered. To determine the charges of particles, the nonlinear Poisson-Boltzmann equation was used, and for the ionization of atoms of the gas phase, the Saha equation taking into account the effect of the displacement of the ionization equilibrium. The dependences of the concentration of electrons and particle charges, as well as the interface between the regions of positive and negative charges of particles, on the concentration of cesium atoms and the concentration of aluminum oxide particles are obtained.

Cosmology

The main features of the universe and its history, and the application of GR to the universe as a whole are presented. The observed near-isotropy and homogeneity of the universe are described, along with a survey of its history. The Saha equation is applied to the recombination process. Cosmic proper time and comoving coordinates are defined, and the form of the metric (Friedmann-Lemaitre-Robertson-Walker) applicable to such a universe is obtained. The main features of the resulting geometry are discussed at length, with a view to both accurate calculation and sound intuition. Redshift and the cosmic expansion are described from several perspectives. Distance measures (luminosity, angular diameter) are defined and the main elements of the observational cosmic distance ladder are outlined.

Cosmological dynamics

The chapter deals with the large-scale dynamics of the universe. First the Friedmann equations are obtained from the Einstein field equation, and they are interpreted with the aid of a Newtonian comparison. Then the application to the universe modelled as a collection of ideal fluids is described. Density parameters and the equation of the state are defined, and the main features of the evolution of matter, radiation and the vacuum are obtained. Analytic solutuions in various simple cases are found. Dark matter and dark energy are defined through their observational evidence. The particle horizon is defined and discussed. The density and temperature at last scattering are calculated by a model involving Thomson scattering, expansion, and the Saha equation.

Production of light nuclei in heavy ion collisions via hagedorn resonances

The physical processes behind the production of light nuclei in heavy ion collisions are unclear. The successful theoretical description of experimental yields by thermal models conflicts with the very small binding energies of the observed states, being fragile in such a hot and dense environment. Other available ideas are delayed production via coalescence, or a cooling of the system after the chemical freeze-out according to a Saha equation, or a ‘quench’ instead of a thermal freeze-out. A recently derived prescription of an (interacting) Hagedorn gas is applied to consolidate the above pictures. The tabulation of decay rates of Hagedorn states into light nuclei allows to calculate yields usually inaccessible due to very poor Monte Carlo statistics. Decay yields of stable hadrons and light nuclei are calculated. While the scale-free decays of Hagedorn states alone are not compatible with the experimental data, a thermalized hadron and Hagedorn state gas is able to describe the experimental data. Applying a cooling of the system according to a Saha-equation with conservation of nucleon and anti-nucleon numbers leads to (nearly) temperature independent yields, thus a production of the light nuclei at temperatures much lower than the chemical freeze-out temperature is compatible with experimental data and with the statistical hadronization model.

A fragmentation model approach for low velocity impact charging

<p>This work addresses the generation of charge during impacts of nano- to microscale projectiles on metal surfaces at speeds from 0.1 to 10 km/s. These speeds are well above the range of elastic deformation and well below speeds where volume ionization occures. Earlier models have utilized impurity diffusion through molten grains together with a Saha-equation to model impact ionization at these speeds. In this work we employ a model of capacitive contact charging in which we allow for projectile fragmentation upon impact. We show that this model well describes laboratory measurements of metal projectiles impacting metal targets. It also can describe in-situ measurements of dust in the Earth’s atmosphere made from rockets. We also address limitations of the currently most used model for impact ionization.</p>