Inner-shell excitation and EXAFS-type phenomena in the chloromethanes

Small angle inelastic scattering of 2.5 keV electrons was used to study the inner-shell excitation of CH4, CH3Cl, CH2Cl2, CHCl3, CCl4 and C2H5Cl in the regions of carbon 1s, chlorine 2p and chlorine 2s excitation. Structure observed below the carbon 1s ionization threshold in each molecule is assigned to promotions of a carbon 1s electron to unoccupied valence and Rydberg orbitals. Trends in the distribution of spectral intensities through the series of chloromethane carbon 1s spectra are discussed in terms of the growth of a potential barrier. Broad features are observed in the chlorine 2p continua of CH2Cl2, CHCl3 and CCl4 and the carbon 1s continuum of CCl4 which are assigned as the energy loss equivalent of extended X-ray absorption fine structure (EXAFS).