Chemische Reaktionskinematik

Abstract

The velocity spectra and cross sections of reactions of the type X*+D2 → XD++D (X+=Ar+, N2 +, CO+) have been found to be independent of the temperature of the target gas ( — 190° to 20°C). The additional forward scattering (as compared to spectator stripping) of the product ion at high energies cannot be explained by the thermal motion of the D2 molecules. A recoil stripping mechanism is proposed. At low energies, an intermediate XD2* is postulated that lives shorter than half a period of rotation and is forward scattered but quickly equilibrates the excess energy among the vibrational degrees of freedom. The reactions of Ar+ and N2 + with CD4 can well be understood by the stripping model over a wide range of energy. At low energies, no preferential forward scattering of the product ion is found as in the corresponding reactions with D2. The strongly unsymmetric broadening of the product ion band together with a small shift to lower velocities indicate a strong interaction of the incident ion with the CD3 group at low energies. The formation of an intermediate complex XCD4 + which isotropically decays is expected at energies of a few tenth of one eV. Direct measurements at such low primary ion energies have not yet been possible.