Product vibrational state distributions in thermal energy associative detachment reactions: F−+H,D → HF(v), DF(v)+e−

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Abstract
Nascent product vibrational state distributions are obtained by the method of spectrally resolved infrared chemiluminescence for the associative detachment reactions: F−+H → HF(v≤5)+e−, ΔH=−238.3 kJ mol−1 and F−+D → DF(v≤7)+e−, ΔH=−245.3 kJ mol−1. These reactions are carried out under thermal energy conditions in a flowing afterglow. The nascent distribution for HF(v) is Nv=1=0.0+0.06−0.0, Nv=2=0.09±0.01, Nv=3=0.21±0.01, Nv=4=0.41±0.02, Nv=5=0.30±0.02 with an average fraction of energy deposited into vibration, 〈fv〉=0.72±0.03 and for DF(v): Nv=1=0.08+0.01−0.07, Nv=2=0.09±0.01, Nv=3=0.15±0.02, Nv=4=0.11±0.02, Nv=5=0.15±0.01, Nv=6=0.24±0.03, Nv=7=0.18±0.02 with 〈fv〉 ≤0.61±0.04. Simple kinematic effects based on angular momentum constraints are not able to explain the broader distribution observed for DF as compared to HF. Several possibilities for this difference are discussed. In an argon buffer, which is much less effective than helium for rotational relaxation, the DF emission exhibits highly nonthermal rotational excitation.