We present the first measurements of ion rotational distributions for photoionization over an extended range ͓0рE K р200 eV for N 2 ͑2 u Ϫ1 ͒ and 3рE K р125 eV for CO ͑4 Ϫ1 ͔͒. The N 2 ion rotational distributions are seen to change dramatically over this energy range, indicating that characteristically molecular behavior of the photoelectron persists far from ionization threshold. In addition, the N 2 and CO results show a strikingly different dependence on energy. Although differences are expected due to the absence of a center of symmetry in CO, detailed calculations reveal that this behavior arises from the presence of Cooper minima in the 2 u →k g continuum in the case of N 2 and from an f -wave shape resonance in the 4 →k channel in CO. Agreement between measured and calculated ion rotational distributions is excellent. The N 2 results are also compared with electron bombardment ionization data. This comparison demonstrates that previous interpretations of electron bombardment data are prone to errors.