Atomic resonance fluorescence spectrometry for rate constants of rapid bimolecular reactions. Part 4.—Chlorine atom fluorescence 4s2,4P–3p52P

Publisher Website
Google Scholar
Abstract
Atomic fluorescence in the vacuum ultraviolet arising from excited multiplet states of Cl(4s4PJ, 4s2PJ and 4s′2DJ) was generated in a flow system by, (a) irradiation of ground state Cl atoms with a chlorine atom resonance lamp, (b) photolysis of Cl2 with a He resonance lamp and (c) impact of Cl2 with He 2s3S1 metastable atoms. For all eight transitions (to the ground 3p5 2PJ states) studied in (a), the intensity of Cl atom resonance fluorescence varied in direct proportion with ground state Cl atom concentration, N, with sufficiently low values of N; for instance, at 138.0 nm this value of N was ⩽ 1 × 1012 cm–3; and at 134.7 nm, N was ⩽ 3 × 1011 cm–3. The most sensitive transitions for resonance fluorescence detection of Cl under the conditions used were the 138.0 nm and the 134.7 nm lines. Atomic fluorescence intensities were measured, and used to derive certain branching ratios for Einstein coefficients for spontaneous emission involving the Cl multiplet transitions, Aλ ki: Aki 139.7/Aki 138.0=(0.13 ± 0.02); Aki 136.3/Aki 134.7=(0.14 ± 0.02) and Aki 135.2/Aki 133.6=(1.7 ± 0.3). A resonance fluorescence technique of high sensitivity for kinetic studies in a flow system (∼200 N m–2 total pressure) is described, giving detection of ground state Cl concentrations down to 3 × 109 cm–3 with signal-to-noise of unity. It was used to measure the rate constant for the extremely rapid reaction of Cl with Br2, Cl + Br2→ BrCl + Br, k298=(1.9 ± 0.2)× 10–10 cm3 molecule–1 s–1.

This publication has 0 references indexed in Scilit: