Dynamics of molecular Penning ionization: angle-energy distributions of N2+ from He*(21S)+N2

Angle-energy distributions resulting from the Penning ionization of N2 by metastable singlet helium He*(21S) at collision energies of 2.5 and 4.4 kcal/mol have been measured using crossed supersonic molecular beams and a rotatable mass-spectrometric detector. Predominantly forward scattering of N2+ is observed, and although substantial backscattering is also present at both energies, the collision intermediates are mainly short-lived. Both the sharpness of the forward-scattering peak and the mean recoil energy increase at the higher energy. The results are compared to quantum scattering calculations based on a recently proposed set of potential surfaces.