Nonequilibrium electron energy distribution in Au under subpicosecond laser irradiation: A kinetic study

We have performed a kinetic study of the electron dynamic relaxation inside a Au film subjected to a subpicosecond laser pulse. For this purpose, we have developed a time-dependent numerical solution of the Boltzmann equation for the electrons inside the film considering the collision integrals due to electron–electron and electron–phonon collisions and a perturbation term due to the laser pulse. Our results show that, after the pulse excitation, electron distributions are very far from equilibrium. Therefore it is not possible, especially in the first part of the temporal evolution, to describe the relaxation of the electron distribution through a two-temperature model

Reduced Two-Level Approach for Air Kinetics in Recombination Regime

Abstract. The possibility of using reduced model, that account for non-Boltzmann vibrational distributions for nitrogen monoxide kinetics has been explored. The basic idea is that the rate coefficients, which are proportional to the tail of the vibrational distribution function, are strictly correlated to reactant density rather than to vibrational temperature, which depend on the low energy distribution. The model consider the rate coefficients as a function of the population of the last vibrational level of the relevant species, which evolution is calculated with a proper kinetic equation

Vibrational kinetics of electronically excited states in H

The evolution of atmospheric pressure hydrogen plasma under the action of repetitively ns electrical pulse has been investigated using a 0D state-to-state kinetic model that self-consistently couples the master equation of heavy particles and the Boltzmann equation for free electrons. The kinetic model includes, together with atomic hydrogen states and the vibrational kinetics of H2 ground state, vibrational levels of singlet states, accounting for the collisional quenching, having a relevant role because of the high pressure. The mechanisms of excitations, radiative decay and collisional quenching involving the excited H2 states and the corresponding cross sections, integrated over the non-equilibrium electron energy distribution function (EEDF) to obtain kinetic rates, are discussed in the light of the kinetic simulation results, i.e. the time evolution during the pulse of the plasma composition, of the EEDF and of the vibrational distributions of ground and singlet excited states

Diversity and dynamics of an interstitial Tardigrada population in the Meloria Shoals, Liguria Sea, with a redescription of Batellipes similis (Heterotardigrada, Batillipedidae)

Quantitative samples of sediment for tbc study of the meiofauna were collected monthly beween March 1996 and February 1997 from a 7-m-deep site in tbc Meloria Shoals, Livorno Italy. In tbc Tuscan Shoals, 16 species of tardigrades were found belonging to tbc families Stygarctidae, Halechiniscidae, and Batillipedidac. Megastygarctides orbiculatus and Actinarctus doryPborus are reported for tbc first time in tbc Mediterranean Sea, and a redescription of Batillipes similis is proposed. Global density of . tbc Tardigrada population fluctuated between 8 ind./10 cm2 in May 1996 and 285 ind./10 cm2 in January 1997. The lowest valite of tbc Shannon-Wiener biodiversity index (H' = 1.09) was found in September 1996, whereas the highest score (H' = 2.46) was obtamed in March 1996. Pielou's evenness index (J) fluctuated between 0.40 and 0.88, values attamed in January 1997 and March 1996, respectively. The study confirms the notion that tbc organogenic detritus of the Shoals represents a very favourable environment for meiofauna) organisms in generai, and Tardigrada in particular

Elementary Processes and Kinetic Modeling for Hydrogen and Helium Plasmas

We report cross-sections and rate coefficients for excited states colliding with electrons, heavy particles and walls useful for the description of H 2 /He plasma kinetics under different conditions. In particular, the role of the rotational states in resonant vibrational excitations of the H 2 molecule by electron impact and the calculation of the related cross-sections are illustrated. The theoretical determination of the cross-section for the rovibrational energy exchange and dissociation of H 2 molecule, induced by He atom impact, by using the quasi-classical trajectory method is discussed. Recombination probabilities of H atoms on tungsten and graphite, relevant for the determination of the nascent vibrational distribution, are also presented. An example of a state-to-state plasma kinetic model for the description of shock waves operating in H 2 and He-H 2 mixtures is presented, emphasizing also the role of electronically-excited states in affecting the electron energy distribution function of free electrons. Finally, the thermodynamic properties and the electrical conductivity of non-ideal, high-density hydrogen plasma are finally discussed, in particular focusing on the pressure ionization phenomenon in high-pressure high-temperature plasmas

Advances in non-equilibrium

Numerous applications have required the study of $$\hbox {CO}_2$$ plasmas since the 1960s, from $$\hbox {CO}_2$$ lasers to spacecraft heat shields. However, in recent years, intense research activities on the subject have restarted because of environmental problems associated with $$\hbox {CO}_2$$ emissions. The present review provides a synthesis of the current state of knowledge on the physical chemistry of cold $$\hbox {CO}_2$$ plasmas. In particular, the different modeling approaches implemented to address specific aspects of $$\hbox {CO}_2$$ plasmas are presented. Throughout the paper, the importance of conducting joint experimental, theoretical and modeling studies to elucidate the complex couplings at play in $$\hbox {CO}_2$$ plasmas is emphasized. Therefore, the experimental data that are likely to bring relevant constraints to the different modeling approaches are first reviewed. Second, the calculation of some key elementary processes obtained with semi-empirical, classical and quantum methods is presented. In order to describe the electron kinetics, the latest coherent sets of cross section satisfying the constraints of “electron swarm” analyses are introduced, and the need for self-consistent calculations for determining accurate electron energy distribution function (EEDF) is evidenced. The main findings of the latest zero-dimensional (0D) global models about the complex chemistry of $$\hbox {CO}_2$$ and its dissociation products in different plasma discharges are then given, and full state-to-state (STS) models of only the vibrational-dissociation kinetics developed for studies of spacecraft shields are described. Finally, two important points for all applications using $$\hbox {CO}_2$$ containing plasma are discussed: the role of surfaces in contact with the plasma, and the need for 2D/3D models to capture the main features of complex reactor geometries including effects induced by fluid dynamics on the plasma properties. In addition to bringing together the latest advances in the description of $$\hbox {CO}_2$$ non-equilibrium plasmas, the results presented here also highlight the fundamental data that are still missing and the possible routes that still need to be investigated