DEPENDENCE OF COLLISION DYNAMICS ON A SHORT-RANGE PART OF INTERACTION POTENTIAL IN A COLLINEAR ATOM-MOLECULE COLLISIONS Kunizo Onda Faculty of Industrial Science and Technology, Science University of Tokyo, Oshamambe, Hokkaido 049-3514, Japan We have investigated a vibrationally inelastic scattering, an atom-exchage reaction, and dissociation processes in atom-diatomic molecule collisions of a collinear configuration at the total energy up to 10 eV. It is clarified that the collision dynamics is extremely sensitive to the short range part of the interaction potential energy surface employed for both the collision systems of He + H$_2^+$ and H + H$_2$.