Computational Study of the Net Emission Coefficient of H₂O–Air–Cu and H₂O–Air–Ni Thermal Plasma

The determination of the radiation emitted by thermal plasmas is a very complex problem due to the temperature gradients, species densities, and their complex distribution. Several methods can be used to calculate the radiation emitted, based on various approaches such as geometrical, spectral, statistical, as well as computational simulations. This article presents the computation of net emission coefficients (NECs) for thermal plasma mixtures of H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O–air–Cu and H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O–air–Ni. The calculations were performed for isothermal, spherical, and homogeneous plasmas, under the assumption of local thermodynamic equilibrium (LTE), at pressures up to 10 atm and over a temperature range of 300–30000 K. The NEC was obtained by summing the various contributions from atomic continua, molecular continua, atomic lines, and molecular bands. The results emphasize the impact of three parameters on the NECs: temperature, pressure, and plasma thickness. They also demonstrate the crucial importance of metallic vapors on low-temperature plasma radiation owing to the low ionization energy of neutral Cu and Ni compared to the neutral species O, H, and N present in H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O and air. The values of NEC allow for the estimation of radiative losses in the hot zones of the plasma, in numerical modeling, especially devoted to laser-induced breakdown spectroscopy (LIBS) applications.