Ion Molecular Collision Measured with a Multi-Hit Detector*

Imad Ali
J. R. Macdonald Laboratory, Kansas State University

We report on the energy and angular distributions of the fragments emitted in the collision of 1 MeV/u F⁸⁺ with N₂. The energies and the emission angle of the fragments is calculated from the measured complete momentum vectors of both fragments emitted in the dissociation of the diatomic Molecule (N₂) using a fast position sensitive multi-hit-detector system. The energy and the emission angle is measured separately for all fragments from the dissociation channels with different charge states. The kinetic energy release of the fragments is discussed on the basis of a Coulomb-explosion model between the ion pairs. It is found that the maxima of the measured energy distributions fit appropriately to the energy evaluated using the Coulomb-explosion model for the fragments from the dissociation states of q₁q₂ < 3 but for higher charge states the measured energy maxima diverges strongly to lower values than the calculated ones. This behavior contradicts with the expectations that the Coulomb-explosion model is assumed to work better for highly stripped molecules. Deposition of energy into highly excited states and screening effects of the electrons remaining in the atomic shells of the exploding charged fragments may be responsible to the low kinetic energy release. The angular distributions show dipole transitions in the case of ionization, but in the case of transfer ionization dipole transitions and higher order transitions may contribute to the angular distributions from many dissociative states of the molecule.