Influence of molecular orientation on the multiple differential cross sections for the (e,2e) process on a water molecule - art. no. 052720

Eightfold and fivefold differential cross sections (8DCS and 5DCS, respecti vely) for the (e,2e) process on a water molecule are calculated within the framework of the fist Born approximation, and the role of the molecular ori entation on the collision process is studied and analyzed. The molecular wa ve functions are described by the linear combination of atomic orbitals (LC AO) (self-consistent-field LCAO molecular orbitals method). We present resu lts for electron impinging at an intermediate energy of 250 eV and in an as ymmetric coplanar geometry and kinematics. When particular molecule orienta tions are chosen, the 8DCS exhibit large differences, in shape as well as i n magnitude. A comparison of these results with an averaged-space calculati on (integration of the 8DCS over Euler angles) confirms the necessity to ta ke properly into account the molecular orientation in the calculations of t he ionization cross sections of polyatomic molecules.