Initial vibrational energy distributions determined by infra-red chemiluminescence

The reaction of atomic hydrogen with molecular fluorine produces vibrationally excited hydrogen fluoride with v′ ? 8>. Maximum population is achieved in v′ = 6. It is estimated that 58 per cent of the available energy of reaction is initially present as HF _v′→0 ^?.

Trajectory calculations have been made using various types of modified London-Eyring-Polanyi-Sato (LEPS) surfaces to obtain the vibrational energy level distributions for comparison with experimental results. A general conclusion is that in all cases, the predicted distribution is too narrow. No one surface could simultaneously give an entirely satisfactory prediction of the product vibrational energy distribution, activation energy with related rate constant and reaction enthalpy. It is concluded that a systematic method of selection of the value for D_e ³ for the first ³Σ state will be necessary if a surface is to be transferred between related reactions. A ‘best’ surface is selected and shown to be compatible with the known activation energy and rate constant values for this reaction.