CROSS-SECTIONS FOR X-RAY AND HIGH-ENERGY ELECTRON-SCATTERING BY SMALLMOLECULES

Ab initio, multi-reference, configuration-interaction (CI) calculation s 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: H2O, NH3, N-2, O-2, B2H6. SiH4 and CO2. Both el astic and inelastic cross sections are considered. We examine the sens itivity of the cross sections to various details of the treatment of e lectron 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 calculati ons. There is fair agreement with experiment except for N-2 and O-2 fo r which previously observed discrepancies remain unresolved. Higher-or der Born corrections should be examined in these cases.