Electron attachment inF2: Conclusive demonstration of nonresonant,s-wave coupling in the limit of zero electron energy

Dissociative electron attachment to ${\mathrm{F}}_2$ has been observed in the energy range 0≤ɛ≤140 meV, at a resolution of 6 meV (full width at half maximum). Results show conclusively a sharp, resolution-limited threshold behavior consistent with an s-wave cross section varying as ${\varepsilon }^{\mathrm{-}1/2}$. Two accurate theoretical calculations predict only p-wave behavior varying as ${\varepsilon }^{1/2}$. Several nonadiabatic coupling effects leading to s-wave behavior are outlined.