Oscillator strength study of the excitations of valence-shell of C2H2 by high-resolution inelastic x-ray scattering

Abstract

The oscillator strengths of the valence–shell excitations of C2H2 are extremely important for testing theoretical models and studying interstellar gases. In this study, the high-resolution inelastic x-ray scattering (IXS) method is adopted to determine the generalized oscillator strengths (GOSs) of the valence–shell excitations of C2H2 at a photon energy of 10 keV. The GOSs are extrapolated to their zero limit to obtain the corresponding optical oscillator strengths (OOSs). Through taking a completely different experimental method of the IXS, the present results offer the high energy limit for electron collision to satisfy the first Born approximation (FBA) and cross-check the previous experimental and theoretical results independently. The comparisons indicate that an electron collision energy of 1500 eV is not enough for C2H2 to satisfy the FBA for the large squared momentum transfer, and the line saturation effect limits the accuracy of the OOSs measured by the photoabsorption method.