The Formation of AlF Molecules and Al Atoms in a C₂H₂/N₂O Flame Studied by Absorption and Emission Spectrometry of Molecules and Atoms

Impact of the chemical form of different fluorine sources on the formation of AlF molecules in a C2H2/N2O flame

“…In the case of HF as a uorine source, the Al atomic absorption at 484.23 nm as well as the AlO molecular emission intensity at 484.23 nm increase linearly with the concentration of HF up to a molar ratio of F : Al around 3 and remains almost constant at the reached signal level at higher molar ratios. As recently shown, 18 this behaviour is explained by the mechanism of Al and AlO formation. Below a molar F : Al ratio of 3 (i.e., in excess of aluminium), two parallel pathways of aluminium atomization occur: (i) a fast pathway via the fractionation of volatile AlF 3 via AlF into Al; and (ii) a slow pathway suggested by Rubeska 19 via the reduction of the oxidic and/or carbidic species AlO x C y by the ame gas constituents.…”

“…It is merely a kinetic effect, because the total quantity of aluminium introduced into the ame is not changed by the presence of uoride. 18 However, having curves similar in shape, H 2 SiF 6 and HBF 4 show a similar effect on Al-containing solutions with signicantly reduced Al AA absorbance and AlO emission intensities in the slope region (Fig. 4), and for H 2 SiF 6 in the plateau region.…”

“…At a molar ratio above 3, Al is entirely transported by uoride into the ame, presumably as volatile AlF 3 . 18 In conclusion, the presence of uorine opens an alternative and faster pathway for Al atomization compared to the oxidic and/or carbidic pathway. It is merely a kinetic effect, because the total quantity of aluminium introduced into the ame is not changed by the presence of uoride.…”

“…All measurements were carried out using a model contrAA 300 high resolution continuum source ame atomic absorption spectrometer (Analytik Jena, Jena, Germany), whose instrumental details are summarized by Welz et al 2 The experimental setup is identical to that in ref. 18. MA data of AlF at a wavelength of 227.66 nm, of SiO at a wavelength of 229.90 nm and of BF at a wavelength of 195.59 nm, as well as AA data of Al at a wavelength of 256.798 nm, B at a wavelength of 249.77 nm and Si at a wavelength of 251.61 nm were obtained by means of a reference spectrum to correct unwanted ame structures by static (AlF, BF, and SiO) or dynamic (Al, B, and Si) background correction with reference measurements.…”

“…The reverse is found in aluminium solutions with and without the addition of hydrouoric acid. [16][17][18] In the absence of hydrouoric acid, aluminium atoms are formed in the C 2 H 2 / N 2 O ame via the reduction of volatile oxidic and/or carbidic species by the ame gases. 19 The presence of HF leads to volatile AlF 3 , which vastly decomposes into AlF molecules and, subsequently, into Al atoms.…”