Determination of the a′-parameter of resonance lines in flames

A method is described for determining experimentally the a′-parameter of resonance lines of Na,K,Li,Cs,Ca and Sr by combining the so-called curves of growth† with duplication curves. Theoretical curves of growth and duplication curves for single lines and doublets (with 1 = 1/3 , 2 = 2/3 ) were calculated for a series of thirteen a′-values ranging from 0 to 5.0, by means of a binary electronic computer. The a′-parameter values for the first resonance lines (and doublets) of the mentioned alkali and alkaline-earth metals were determined experimentally in air-CO and air-C2H2 flames at atmospheric pressure with temperatures ranging from 2000 to 2500°K. The corresponding cross-sections for adiabatic collisions were derived and compared with the available literature data. Additional conclusions were drawn as regards the formation of alkali-and alkaline-earth molecules in these flames. The possible influence of side-effects, such as (hyper)-fine structure, resonance broadening, broadening due to quenching collisions, radiative disequilibrium and the variation of the index of refraction, will be briefly dealt with