K-shell excitation of HF and F2 studied by electron energy-loss spectroscopy

The fluorine K-shell (1s) excitation spectra of HF and F2 have been studied by small-angle inelastic scattering of 2.5 keV electrons. The F2 spectrum exhibits a dramatic 1s to sigma * shape resonance 14.5 eV below the F 1s ionisation threshold which is qualitatively different from the 1s to sigma * transitions observed in all other first-row diatomics. An empirical correlation between experimental term values for both sigma * and pi * K-shell …