Determination of absolute densities of B, Al, Ga and Si atoms in non-equilibrium plasmas from relative intensities in resonance multiplets distorted by reabsorption

Abstract

The approach proposed recently as a spectroscopic tecnique of a boron density determination in microwave plasma has been expanded for B, Al, Ga, Si atoms and generalized. The method is based on measurements of relative intensities of pairs of spectral lines belonging to resonance multiplets having common upper level. It is shown that when the reabsorption of the lines within plasma is sufficient, then the intensity ratios depend on the gas temperature T and the product NL of total density of the ground state atoms N and a length of a plasma column L. Thus in the case of the B, Al, Ga doublets the temperature T should be known. The resonance multiplet of Si (three independent intensity ratios) provides an opportunity to obtain both T and N and even to organize internal check of the applicability of the proposed method to certain plasma conditions. The ratios were calculated for resonance lines of B, Al, Ga and Si under T=300-2400 K and NL=10^7-10^15 cm^(-3) m. The results of numerical calculations and ranges of applicability of the method are discussed.