Theoretical Calculation of Optical Collisional Cross Sections and α-Parameter Values for Transitions of Interest in Atomic Absorption Spectrometry

Abstract

A method has been developed for calculating optical collisional cross sections and subsequent a-parameter values for spectral transitions of interest to analytical atomic spectroscopists. A combination of classical and semiclassical line broadening theory is used. The calculated values compare well (±20% or less) with values determined experimentally for elements without extensive hyperfine structure. If hyperfine structure is significant, the calculated a-parameter can be used to calculate the full width at half maximum of the spectral transition, but not the actual shape. The cross section values are found to correlate well with the proximity of the energy of the excited state of the atom to the ionization energy and to the orbitals involved in the electronic transition (e.g., s-p). A method of converting a values to different flame conditions has also been developed. Cross sections and a-parameter values for a total of 114 transitions from 52 elements have been calculated for the air-acetylene flame.