Abstract

Excitation of v' = 3 in A²Σ⁺ OH is popular for flame LIF measurements, in part because of the reduced influence of collisional effects on this rapidly predissociating level. However, at atmospheric pressure a large fraction (over 50%) of the total light emitted can originate from levels populated by vibrational transfer from v' =3. Fluorescence scans following laser excitation of v′ = 3 made in the burnt gases of flames between 14 and 760 Torr show an increasing population in v' = 0, 1, 2 with increasing pressure. H₂/O₂ flames where H₂O is the primary collider show the least transfer, CH₄/O₂ (H₂O and CO₂) more, and CH₄/air (with N₂ collider, efficient for VET but poor at quenching) the most. There is a small decrease in VET with increasing ro­tational level.

© 1992 Optical Society of America