Electron Attachment to van der Waals Molecules

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Electron attachment to van der Waals molecules is of great importance not only in a fundamental reaction process in gas phase but also in various phenomena in ionized gas. Very recently, our group has obtained some peculiar phenomena in electron attachment process in gas phase, which has been interpreted in terms of an attachment process to van der Walls moleules. The objectives of the present project are to elucidate a fundamental mechnizm of the peculiar phenomena in the electron attachment to van der Waals molecules and to extract general rules which governs the process in various reaction kinetics.In this work, first, electron attachment to isolated moleules of O_2, N_2O, NO, NO_2, SO_2, C_3O_2, and some alkyl halides has been studied in detail using a microwave conductivity technique combined with a pulse radiolysis 1method. The absolute values of rate constants of the attachment process to the molecules have been obtained elucidating the mechanizm of the attachment process. Furthermore, pressure dependence and temperature dependence of the rate constants have been obtained, in which electron attachement to van der Waals molecules are clearly observed.In order to extend the study described above by means of a more direct method, we have constracted an apparatus of a low energy electron energy loss spectroscopy from van der Waals molecules produced in a supersonic expansion. We have already obtained electron energy loss spectra and scattering angular dependence of the spectra for isolated atoms and molecules using a convensional effusive nozzle, and confirmed efficient production of van der Waals moleules and van der Waals clusters in supersonic nozzle expansion.