2D-measurement of Penning ionization cross section upon molecular orientation and collision energy in Ar(P-3(2,0))+CHCl3 crossed beam reaction

The Penning ionization cross section of Ar* + CHCl3 crossed beam reaction i s determined as the function of both molecular orientation and relative col lision energy using oriented CHCl3 molecular beam and TOF measurement. We f ind that the steric opacity function at low collision energies is well corr elated to the exterior electron density distribution of the CHCl3 molecular orbital that plays a key role in the electron exchange. At high collision energies, however, the reactivity along the molecular axis becomes favorabl e while the sideways approach on the other hand becomes unfavorable. The re sult of our ab initio calculation reveals that this collision energy depend ence of the sideways approach shows clear discrepancy with the generally ac cepted propensity rule for repulsive interaction potential. We propose here that this discrepancy Can be ascribed to the dependent competition of prod uct branching between Penning ionization and that neutral dissociation vari es as collision energy.