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 Nv 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.