Requirements are outlined for a suitable set of dynamic orbitals for theoretical studies in collision problems. The effect of these upon the wave function, dynamic energy correction, and effective internuclear potential are all considered. It is shown that earlier forms suggested for this type of problem do not meet all required dynamic boundary conditions, principally because of their failure to recognize that physically, for moderate speed collisions, the electron at times "belongs" to the "molecule" proper and not to either atom individually. The earlier orbitals also fail to make allowances for the reluctance of an electronic charge distribution to follow rapid rotation of an internuclear axis. These considerations suggest a new form of dynamic orbital which by remedying these deficiencies automatically achieves complete orthonormality. The results of preliminary charge transfer calculations with the new orbital basis are presented.

• Received 15 January 1969

DOI:https://doi.org/10.1103/PhysRev.181.311