Electron-bombardment matrix isolation and PEPICO studies as complementary techniques in ion chemistry: an FTIR study of the decomposition of the vinyl fluoride cation

FTIR spectra have been obtained for matrices formed following electron bombardment of gas mixtures containing varying amounts of vinyl fluoride (VF) in Ar (1:400 to 1:25,600; VF/Ar). The major matrix-isolated products are a π-complex of HF/C(2)H(2) , fluoroacetylene (HC≡CF) and two isomers of C(2)H(2)F(•). These products correspond well with the products of photoionization of VF near 15.8 eV. These observations support the dominant mechanism of ionization in the EB-MI environment as charge transfer of the substrate molecule to Ar(•+). Some differences are noted between the observed EB-MI products and the results from PEPICO studies, primarily in that the EB-MI products are observed as neutralized forms. The close correlation in EB-MI and photoionization results allows the EB-MI technique to be utilized as an ion structural analysis tool in complement to PEPICO studies, and allows the use of PEPICO studies to help predict and elucidate high-pressure chemistry mechanisms through EB-MI studies. The differences in the EB-MI results and ions observed using the PEPICO technique are rationalized in terms of the differences in the experimental techniques. Using VF as the test system, reagent partial pressure conditions that best complement PEPICO studies are determined. Although the major results are observed for all VF partial pressures, dilute samples give rise to further ionization of the primary products, and more concentrated samples give rise to radical-radical reaction chemistry. As a result, a nominal range of 1:3200 (VF/Ar) is demonstrated to provide the best correlation with the gas-phase PEPICO measurements.