Intensity oscillations in the carbon 1s ionization cross sections of 2-butyne

• Published in: The Journal of chemical physics 2013-06, Vol.138 (23), p.234310-234310
• Main Authors: Carroll, Thomas X, Zahl, Maria G, Børve, Knut J, Sæthre, Leif J, Decleva, Piero, Ponzi, Aurora, Kas, Joshua J, Vila, Fernando D, Rehr, John J, Thomas, T Darrah
• Format: Article
• Language: English
• Subjects: ABSORPTION SPECTROSCOPY; ATOMIC AND MOLECULAR PHYSICS; CARBON; Carbon - chemistry; Chlorine; CROSS SECTIONS; DENSITY FUNCTIONAL METHOD; ELECTRONS; ENERGY DEPENDENCE; EV RANGE 100-1000; FINE STRUCTURE; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; Ions - chemistry; Mathematical models; MUFFIN-TIN POTENTIAL; MULTIPLE SCATTERING; ORGANIC COMPOUNDS; OSCILLATIONS; PHOTOELECTRON SPECTROSCOPY; PHOTOIONIZATION; PHOTONS; Scattering; Scattering, Radiation; Spectra; Thresholds; X-RAY SPECTROSCOPY
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.4810870

Carbon 1s photoelectron spectra for 2-butyne (CH3C≡CCH3) measured in the photon energy range from threshold to 150 eV above threshold show oscillations in the intensity ratio C2,3/C1,4. Similar oscillations have been seen in chloroethanes, where the effect has been attributed to EXAFS-type scattering from the substituent chlorine atoms. In 2-butyne, however, there is no high-Z atom to provide a scattering center and, hence, oscillations of the magnitude observed are surprising. The results have been analyzed in terms of two different theoretical models: a density-functional model with B-spline atom-centered functions to represent the continuum electrons and a multiple-scattering model using muffin-tin potentials to represent the scattering centers. Both methods give a reasonable description of the energy dependence of the intensity ratios.