Irradiation of gold nanorods can lead to the formation of several new nanostructures. One of the most interesting among them are phi-shaped rods, a stable intermediate shape in the rod-to-sphere conversion process, but not much attention has been paid to their characterization. In this work, we irradiated colloidal rods, looking for the conditions to maximize the generation of phi-shaped structures. The shape and dimensions of the irradiated samples were then statistically analyzed. Moreover, we have calculated the energy range within which such transformation into phi-shaped rods takes place, which has been determined to be a very narrow energy window (between 0.38 and 0.41 eV/atom). Finally, we have performed simulations to characterize the optical response of such structures.