PHOTOELECTRON-INDUCED DISSOCIATIVE ATTACHEMENT IN $C_{2}H_{2} D_{0} (HCC-H)$
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Date
1990
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Ohio State University
Abstract
Photoelectrons generated in the photoinonization of acetyiene are observed to produce G2H- upon collision with other $C_{2}H_{2}$ molecules. The photoelectron energy can be continously tuned from O- SeV by varying the incident photon energy from 11:40 eV (the ionization potential of $C_{2}H_{2}$) to higher energy. The dissociative attachement process $e + C_{2}H_{2}- C_{2}H^{-} + H$ has a threshold at $877\pm 2{\AA}$ corresponding to a photoelectron energy of $2.74 \pm 0.03 eV$. The same threshold value has been obtained at $298^{\circ}K$ and $-150^{\circ}K$, and hence the temperature dependence, if any, is slight. When this threshold is combined with E.A. $(C_{2}H_{2}) = 2.969\pm 0.010 eV$, one obtains $D_{0} (HC_{2} - H) 5.71 \pm 0.03 eV = 131.6 \pm 0.7 Kcal/mol$.
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Author Institution: Argonne National Laboratory