We report the first full analysis of collisionally induced atomic alignment and orientation for a molecular collision process. In an experiment with crossed supersonic beams of N 2 and laser excited Na(32ps/2) we have studied the dependence of angular and energy resolved differential quenching cross sections as a function of the linear and circular polarization of the exciting laser light. The anisotropies observed in the linear polarization data range up to 2:1 when corrected for electron and nuclear spin relaxation. The maximum effect is found at small scattering angles and intermediate energy transfer where the cross section is also largest. The atomic alignment angle most favourable for quenching relates to the scattering angle and can be understood in a model picture in such a way that the (NAN2)* molecular system is formed at internuclear distances as low as R = 10a 0. The circular asymmetry is small but with significant structure and is attributed to interaction on different potential surfaces at R>10a o. Full analysis of the four measurable parameter is given in terms of the density matrix in a frame with z-axis perpendicular to collision plane which allows a clear understanding of the properties of atomic reflection symmetry and coherence of the scattering process.

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