Screening corrections for calculation of electron scattering from polyatomic molecules

The quasifree nonempirical model proposed by Staszewka et al. in 1983 for the imaginary part of the electron scattering optical potential is revised, in order to improve its foundations, accuracy, and range of applicability. The importance of relativistic and many-body effects for heavy atoms is shown and some corrections proposed. A criterion for selecting the {delta} parameter is discussed. The model is also shown to admit considerable simplifications without loss of accuracy. Calculated elastic (differential and integral) and inelastic cross sections for He to Xe noble gases and also for N{sub 2}, CO, and CO{sub 2} molecules are compared to experimental values.

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Improvements on the quasifree absorption model for electron scattering

Differential and integral cross sections for elastic electron collisions with uracil, cytosine, guanine, adenine and thymine have been calculated using the independent atom method with a static-polarization model potential for incident energies ranging from 50 to 4000 eV. Total cross sections for single electron-impact ionization of selected DNA and RNA bases have also been calculated with the binary-encounter-Bethe model from the ionization threshold up to 5000 eV. Cross sections within the investigated energy range, can be related to the molecular symmetry, the number of target electrons and molecular size; elastic and ionization processes are most efficient for guanine and adenine molecules, while the lowest cross sections were obtained for the uracil molecule. The ionization cross sections for cytosine, thymine, adenine and guanine are compared with those recently obtained with a semi-classical and binary-encounter-Bethe formalisms. No theoretical and experimental data for elastic electron scattering from DNA and RNA bases are available, but comparisons with calculations for molecules of similar size and geometry allows the validity of the theoretical approach to be verified.

Cross section calculations for electron scattering from DNA and RNA bases.

Screening corrections for calculation of electron scattering differential cross sections from polyatomic molecules

Improvements on the imaginary part of a non-empirical model potential for electron scattering (30 to 10000 eV energies)

Additivity rule for the calculation of electron scattering from polyatomic molecules

The previously used additivity rule has been modified by considering the geometric shielding effect of molecules. Total cross sections (TCSs) for electron scattering from hydrocarbon molecules and are calculated in 10 - 1000 eV employing this semi-empirical approach. The atoms are presented by spherical complex optical potential which is composed of static, exchange, polarization, and absorption terms. Compared with our earlier results, the modified additivity rule for the TCS on complex polyatomic molecules is simple but more effective and it yields better accord with experiments in the intermediate and high energy region.

Yuhai Jiang

Papers

Additivity rule for the calculation of electron scattering from polyatomic molecules

Simple model for the calculation of total cross sections for electron scattering from polyatomic molecules

Total cross sections for electron scattering by molecules

Electron scattering by SF6 molecules at intermediate energies

Geometric shielding effects of electron scattering from polyatomic molecules