Anions in laser-induced plasmas

Abstract

The equation of state for plasmas containing negative atomic and molecular ions (anions) is modeled. The model is based on the assumption that all ionization processes and chemical reactions are at local thermal equilibrium and the Coulomb interaction in the plasma is described by the Debye-Hückel theory. In particular, the equation of state is obtained for plasmas containing the elements Ca, Cl, C, Si, N, and Ar. The equilibrium reaction constants are calculated using the latest experimental and ab initio data of spectroscopic constants for the molecules CaCl 2 , CaCl, Cl 2 , N 2 , C 2 , Si 2 , CN, SiN, SiC, and their positive and negative ions. The model is applied to laserinduced plasmas (LIPs) by including the equation of state into a fluid dynamic numerical model based on the NavierStokes equations describing an expansion of LIP plumes into an ambient gas as a reactive viscous flow with radiative losses. In particular, the formation of anions Cl -, C -, Si -, Cl À 2 , Si À 2 , C À 2 , CN -, SiC -, and SiN -in LIPs is investigated in detail.

CaCl and CaF emission in LIBS under simulated martian conditions

“…This is in line with plasma simulations, which usually find that the formation of molecules happens within a comparatively low and narrow temperature range, e.g. 3000-7000 K for CaCl (Shabanov and Gornushkin, 2016).…”

Spatiotemporal characterization of the laser-induced plasma plume in simulated Martian conditions

“…The plasma is then fully described by its temperature and electron density, the number densities of the atoms of each element, and the effective path length of emission and absorption. While this model can work reasonably well for strongly confined plasma plumes in high-pressure noble gas atmospheres, it usually fails to describe LIBS spectra sufficiently because of the inhomogeneous and transient nature of the plasma plume, which can result in spectral features of ions, atoms, and molecules that are only found at significantly different temperatures [22][23][24]. One frequently used modification of this model is therefore to describe the plasma plume as a two-layer system with a hot central layer and a colder peripheral layer, which may also have a different density [25,26].…”

icMRCI+Q Study of the Spectroscopic Properties of the 14 Λ-S and 49 Ω States of the SiN− Anion in the Gas Phase

“…Consequently, SiN − is a tantalizing potential interstellar anion candidate [ 5 ]. Furthermore, the SiN − anion is a compound of considerable importance in gas-phase ion chemistry [ 6 ], laser-induced plasmas [ 7 ], semiconductor chemistry [ 8 ], and microelectronics [ 9 ]. However, very few experiments [ 10 ] and computations [ 11 , 12 , 13 , 14 , 15 , 16 ] have been conducted for its spectroscopic properties.…”