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Semi-empirical R-matrix studies of dissociative electron attachment to several polyatomic molecules

Robyn Shane Wilde, University of Nebraska - Lincoln


In this study we employ a semi-empirical R-matrix method to calculate vibrational excitation (VE) and dissociative electron attachment (DA) cross sections for several polyatomic molecules. The molecules studied here, CH 3Cl, CH3Br, CH3I and CF3Cl, all belong to the class of molecules which can be modelled by assuming only one vibrational mode is excited by low energy electron impact. The present R-matrix model, which employs a connection with the non-local complex potential (NCP) method, is based on this assumption and employs parameters obtained from fitting to experimental data on VE, or other experimental measurements, to provide the input data for calculations of the DA cross sections. ^ The DA cross sections in these molecules vary over an extremely large range and it is seen here that this is mainly due to the difference in the crossing point of the neutral and anion potential curves for the different molecules. This crossing point also determines the temperature dependence of the DA cross sections as well as the thermal electron attachment rates. ^ Vibrational (nuclear-excited) Feshbach resonances have been observed experimentally in CH3I and here we show that such resonances should be common for all of the methyl halides. We discuss the effect of the parameters of the R-matrix theory on the shape of these resonances and in general on the DA cross sections. We also compare the DA cross sections and attachment rates for the molecules studied here. ^ The present work will help with the understanding of low energy electron attachment to polyatomic molecules, a process which has many practical applications. It also provides a basis for the future study of more complicated molecules as well as related phenomena, such as dipole-supported states and electron attachment near a surface or in a bulk medium. ^

Subject Area

Physics, Molecular

Recommended Citation

Wilde, Robyn Shane, "Semi-empirical R-matrix studies of dissociative electron attachment to several polyatomic molecules" (2000). ETD collection for University of Nebraska - Lincoln. AAI9967418.