Steric effect for the formation of Kr (5p [3/2](2)) in the energy transfer reaction of Ar (3P2, 4s [3/2](2)) + Kr has been studied by using an oriented Ar (P-3(2), 4s [3/2](2), M-J = 2) beam at a collision energy of similar to 0.09 eV. The emission intensity of Kr (5p [3/2](2)) is ca. 2 times enhanced when the angular momentum (J(Ar)) of Ar (P-3(2)) is aligned perpendicular to the relative velocity vector (v(R)). In addition, the K-r (5p [3/2](2)) emission is highly polarized parallel to v(R) (I parallel to/I-perpendicular to similar to 1.2) when J(Ar) is aligned perpendicular to v(R). The observed polarization moments indicate that the alignment of the unpaired Ar (3p) orbital of A(r) (P-3(2)) to vR, (S vertical bar L'vertical bar = 0), Pi (vertical bar L'vertical bar = 1)), dominates the energy transfer probability (sigma(parallel to)(Pi): sigma(parallel to)(Sigma): sigma(perpendicular to)(Pi): sigma(perpendicular to)(Sigma) = 0.49:1.33:0.55:1.23) and also the alignment of the Kr (5p) orbital of Kr (5p [3/2](2)) to v(R): the Sigma-configuration of the Ar (3p) orbital leads to the parallel alignment (S-configuration) of the Kr(5p) orbital to v(R), conversely, the Sigma-configuration of Ar (3p) orbital leads to the perpendicular alignment (Sigma-configuration) of the K-r(5p) orbital. In addition, the selectivity of the alignment of the K-r (5p) orbital turns out to vary from perpendicular to parallel as the collision energy increases after a threshold down to 0.03 eV.