Wing profile measurements of the Na-doublet lines in C 2H 2/O 2/N 2, H 2/O 2/N 2 and H 2/O 2/Ar frames at 1 atm

Abstract

Fluorescence-excitation (wing) profiles of the Na- D doublet lines were measured over a wavelength range extending from 0.3 to 200 Å from the line center for the red D 1 and blue D 2 wings and from 0.3 to 3 Å for the red D 2 and the blue D 1 wings, respectively. The line profiles were determined with the aid of a tunable CW dye-laser as a background source by measuring the total fluorescence intensity observed on detuning the laser wavelength. The flames were premixed, laminar, shielded flames at 1 atm, with temperatures ranging from 1860 to 2270 K; N 2 and Ar served as diluent gases. The line core and near-wing profiles (i.e. the region covering 0.3<Δλ<7 Å for the outer wings and 0.3<Δλ<3 Å for the inner ones) in all of the flames studied appeared to have the same frequency dependence, regardless of the nature and concentrations of the gases used. The blue D 2-line profile followed an unexpected (-2.2) law, while the other three profiles obeyed the theoretically expected (-2) law (the dispersion profile function). The line profile in the Δλ range between the impact and quasistatic regions was found to depend on the main perturbers involved. We found that the far blue D 2- and red D 1-wings in the Ar-diluted H 2/O 2 flame obeyed the (- 5 4 ) and (- 3 2 ) laws, respectively, as predicted by the quasi-static theory for the Lennard-Jones interaction. For the N 2-diluted C 2H 2/O 2 and H 2/O 2 flames, we did not find these wing dependences in the Δλ range investigated.