Experimental investigation of the triple differential cross section for electron impact ionization of N2 and CO2 molecules at intermediate impact energy and large ion recoil momentum

• Published in: Journal of physics. B, Atomic, molecular, and optical physics Vol. 42; no. 23; pp. 235205 - 235205 (6)
• Main Authors: Lahmam-Bennani, A, Staicu Casagrande, E M, Naja, A
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 14.12.2009; Institute of Physics
• Subjects: Atomic and molecular collision processes and interactions; Atomic and molecular physics; Electron scattering; Exact sciences and technology; Molecular excitation and ionization by electron impact; Physics; Molecular orbital; Inorganic compounds; Electron impact ionization; Triply differential cross section; Carbon dioxide; Theoretical study; Momentum; Diatomic molecules; Electron-molecule collisions; Nitrogen; Born approximation; Continuum; Nitrogen Molecules; Momentum transfer; Angular distribution; Carbon molecules; Triatomic molecule
• ISSN: 0953-4075; 1361-6455
• DOI: 10.1088/0953-4075/42/23/235205

The (e,2e) triple differential cross sections (TDCS) are measured for the ionization of nitrogen and carbon dioxide molecules in a coplanar asymmetric geometry for a wide range of ejected electron energies and at an incident energy about 500-700 eV. This kinematics corresponds to a large momentum imparted to the ion, and is meant to enhance the recoil scattering. The experimental binary and recoil angular distributions of the TDCS are characterized both by a shift towards larger angles with respect to the momentum transfer direction and by a large intensity in the recoil region, in particular for the ionization of the 'inner' N2(2sigmag) molecular orbital. The data are compared with the results of calculations using the first Born approximation-two centre continuum (FBA-TCC) theoretical model for treating differential electron impact ionization. The experimentally observed shifts and recoil intensity enhancement are not predicted by the model calculations, which rather yield a TDCS symmetrically distributed around the momentum transfer direction, and completely fail in describing the recoil distribution. It is hoped that these new results will stimulate the development of more refined theories for correctly modelling single ionization of molecules.