Dissociative Recombination and Excitation of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{CH}\,^{+}_{5}$ \end{document} : Absolute Cross Sections and Branching Fractions

Abstract

The heavy-ion storage ring CRYRING was used to measure the absolute dissociative recombination and dissociative excitation cross sections for collision energies below 50 eV. Deduced thermal rates coef-cients are consistent with previous beams data but are lower by a factor of 3 than the rates measured by means of the owing afterglow Langmuir probe technique. A resonant structure in dissociative recombination cross section was found at 9 eV. We have determined the branching fractions in DR of below 0.2 eV. The branching is dominated by three-body and dis-CH 5 `CH 3 ] H ] H CH 2 ]H 2 ]H sociation channels, which occur with branching ratios of B0.7 and B0.2, respectively ; thus methane is a minor species among dissociation products. Both the measured absolute cross sections and branching in dissociative recombination of can have important implications for the models of dense interstellar CH 5 clouds and abundance of and in these media. CH 2 , CH