Absolute Oscillator Strengths From the K-Shell Spectra of Fluoroethenes and 1,3-perfluorobutadiene

Absolute oscillator strengths in the region of carbon and fluorine K-shell excitation have been derived for CH2CH2, CH2CHF, cis-CHFCHF, CH2CF2, CHFCF2, CF2CF2, 1,3-C4H6, and 1,3-C4F6 from electron-energy-loss spectra recorded under dipole-dominated conditions. The methods used to derive absolute oscillator strengths from relative energy-loss intensities are discussed in detail. The accuracy of the procedures is tested through comparisons with literature results for N2, CO, and CO2. The total C 1s→π* and C 1s→σ*(C—F) intensities increase systematically as the degree of fluorination increases. The spectra are discussed in terms of bond-length correlation and potential barrier concepts.