Infrared chemiluminescence using a SISAM spectrometer. Reactions producing vibrationally excited HF

Abstract

A SISAM (spectromètre interférential à sélection par l'amplitude de modulation) has been used to observe infrared chemiluminescence from vibrationally excited HF formed in the reactions of F atoms with H₂ and H₂O₂, and of O atoms with C₂HF₃. In experiments on F + H₂→ HF(v⩽ 3)+ H, conditions could be reached where the nascent relative vibrational populations could be determined as N₃: N₂: N₁= 0.31 ± 0.03: 0.48 ± 0.03: 0.21 ± 0.03, in good agreement with previous measurements. Similar measurements on the F + H₂O₂ system gave N₄: N₃: N₂: N₁= 0.15 ± 0.03: 0.25 ± 0.03: 0.31 ± 0.03: 0.30 ± 0.03 for the N_v distribution from the primary reaction F + H₂O₂→ HF(v⩽ 4)+ HO₂. Only weak emission from HF(v= 5), and none from higher levels, could be detected under conditions where the secondary reaction, F + HO₂→ HF(v⩽ 9)+ O₂, should occur. It seems that this reaction does not populate the higher HF levels preferentially, probably because it proceeds via an (HOOF)⁺ complex. The HF(v) emission in the last system is assigned to the products of the highly exothermic secondary reaction O + CHF → HF + CO. Emission could be detected only from HF(v⩽ 3), yielding the relative populations N₃: N₂: N₁= 0.18 ± 0.02: 0.23 ± 0.03: 0.59 ± 0.06. Finally, a short assessment of the use of SISAM spectrometry in infrared chemiluminescence experiments is presented.