The attachment of low energy (9-80 meV) electrons to clusters of nitric oxide (NO) has been studied by means of Rydberg electron transfer (RET) from selected nd states of rubidium (n = 15-40). The product negative ions have stoichiometry (NO)(x)(-) (x = 2-60) and exhibit even/odd intensity alternations (odd > even) which increase in magnitude with cluster size such that only odd cluster ions are observed for x greater than or similar to 20. The experimental data are consistent with an evaporative attachment mechanism in which the production of odd cluster ions is kinetically favored due to differences in stabilities between odd and even cluster ions. These differences in stabilities are attributed to the spin pairing of valence electrons which results in extensive dimerization of NO in condensed phases. It is postulated that, for x > 3, the excess electron becomes localized to form an (NO)(3)(-) ion which is solvated by NO dimers. Interaction potentials governing the initial electron capture process are also discussed.