Some Experimental Evidence of Collision Processes in Spectrochemical Analysis

Abstract

Synthetic silicate melts of CaSiOa and CaMg(SiO₃)₂ and 20 intermediate mixtures were used as standards for Calibrating a spectrochemical analysis method for CaO and MgO by the Ge metal dilution method previously described. The slope of log RET: log C curves showed large departures from unity, as follows: 0.82, 0.73, 0.62, and 0.24 respectively for Mg I 2779, Mg I 2776, Mg II 2795 and Mg II 2798. Curves for all Si lines showed slopes greater than unity: 1.27, 1.8, 4.22, and 6.39 respectively for Si I 2528, Si I 2987, Si I 2881, and Si I 2631. These results had earlier been interpreted as evidence for the effect of “collisions of the second kind” on intensity of light radiated by a DC arc source, whereby Mg and Si atoms collide and excitation energy is transferred from Mg to Si. Si intensity is enhanced and Mg weakened as the population of Mg atoms increases in the arc. The experimental log RET: log C curves are presented for the series of diopside: psuedo-wollastonite standards. The only variable in the standards is the MgO/CaO ratio. The amounts of these two substances vary such that their sum remains approximately constant. The Ge matrix and atmosphere are constant, and the SiO₂ content is nearly so. Since the slopes of the Ca line curves are nearly unity, Mg and Si atoms are concluded to be involved in the energy exchanging collisions.