The ionic potential for the system K + Br_{2} K^{+} + Br_{2}^{-} is given by a Rittner potential of the form
U_{ion}(R) | = | ||
(E1) |
(E2) |
Figure A05-m4bii-F1: K + BR_{2} ionic and covalent potential. |
For a system with the potential given above, the deflection function turns out to be closed. Figure A05-m4bii-F1 represents the deflection curves for chemi-ionization scattering of K + Br_{2} (CM system).
The full curves represent the classically calculated scattering angle for ``ionic'' and ``covalent'' scattering at colliding energies of 10.35 and 6.9 eV, determined using a simple classical model and measurements of the differential cross section in a molecular beam experiment. The dashed curves show the ``pure inelastic'' scattering-angle contribution to the full-line curves.
Figure A05-m4bii-F2: K + BR_{2}, deflection curves for chemi-ionization scattering (CM system. |
The differential cross section calculated based on the deflection function given above has the following shape: Figure A05-m4bii-F3 represents the classically calculated determined chemi-ionization differential cross section of K + Br_{2} (CM system) at colliding energies of 6.9 and 10.35 eV and convoluted with the energy spread of the velocity selector.
Figure A05-m4bii-F3: K + BR_{2}, classically calculated chemi-ionization differential cross section (CM system) at colliding energies of 6.9 eV and 10.35 eV. |
For both energies equal units have been used on the ordinate. The dotted lines indicate the dependence of the slope steepness for ``covalent'' scattering. At E_{i}= 10.35 eV and different values of the polarizability , and the ionic-well minimum the positions of the scattering angle for b=R_{c}scattering respectively the classical rainbow angle have been indicated along the abscissa. The values used in the calculations have been underlined.