Laser-induced fluorescence studies of excited Sr reactions. III. Sr(3P1)+CHF=CH2, CF2=CH2, CHF=CHF, and C6H5F

Laser-induced fluorescence spectra reveal the internal energy distributions of SrF(X 2Σ) formed in the reactions of electronically excited Sr(3P1) with various unsaturated fluorohydrocarbons, i.e., CHF=CH2, CF2=CH2, CHF=CHF, and C6H5F. The internal energy distribution of the ground state diatomic product typically shows less vibrational excitation, without inversion, and somewhat lower rotational excitation than the reactions of Sr(3P1) with HF and saturated hydrocarbons. The different behavior of the two groups of reactants is rationalized by a simple MO picture, assuming that an electron from Sr is transferred to a σ* orbital in HF and the saturated fluorohydrocarbons and to a π* orbital in the unsaturated fluorohydrocarbons with a subsequent transfer to a σ* orbital of the C–F bond. The latter transfer constitutes an extension of the reaction path, leading to less vibrational excitation. This would explain why the energy disposal in the reaction with C6H5F behaves similar to that in the reactions with the fluoroethenes. Even if the shape of the vibrational distribution of the SrF product is the same for all unsaturated fluorohydrocarbons studied, the degree of vibrational excitation varies strongly. This even holds when comparing cis- and transCHF=CHF, where the distributions can be characterized by distinct surprisal parameters.