Steric factors greater than 1 or less than 0?

From my understanding, the steric factor accounts for the relative orientation required by reactants in order to react in collision theory. This implies that steric factors should probably always be below 1 and above 0, since the relative orientation logically should always be a limiting factor, but below 0 or equal to 0 would mean that the reaction cannot take place.


However, my textbook, as a thinking point, asked if there could be a case where the steric factor is more than 1. Specifically, the example it gave was the harpoon mechanism between potassium and the iodine molecule.


My question is, can the steric factor be above 1 or less than 0, and how does that apply to the harpoon mechanism?


