Dissociative Electron Attachment inI2Vapor at 295° K

Abstract

Two-body electron attachment frequencies have been determined for iodine in the presence of helium using microwave cavity techniques where initial ionization is produced by a single light pulse from a hydrogen lamp. The value for the electron attachment coefficient determined from the attachment frequency data is $k=1.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ ${\mathrm{cm}}^{3}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ at 295\ifmmode^\circ\else\textdegree\fi{}K. The ambipolar diffusion of iodine ions in helium has also been examined at this temperature, and a value for ${\mathrm{D}}_{a}+p$ of 730 ${\mathrm{cm}}^{2}$/sec Torr was obtained. Electron-density decay rates observed using a repetitive-pulse technique were higher than those observed using the singlepulse technique for a given iodine vapor pressure. Possible effects on the electron diffusion rate as a result of the presence of negative ions are discussed.