Cross sections for x-ray and high-energy electron scattering by small molecules

Ab initio , multi-reference, configuration-interaction (CI) calculations of first Born cross sections for high-energy electron scattering and Waller-Hartree cross sections for x-ray scattering are presented for seven small molecules: , , and . Both elastic and inelastic cross sections are considered. We examine the sensitivity of the cross sections to various details of the treatment of electron correlation, such as the use of single- versus multi-reference CI methods, perturbative corrections to them, and the choice of basis set. There is good agreement between these and previous MRCI calculations. There is fair agreement with experiment except for and for which previously observed discrepancies remain unresolved. Higher-order Born corrections should be examined in these cases.