A line-tunable CO laser has been used to record infrared absorption profiles for (NO)n+ and (NO)(n)(+).Ar clusters for n in the range 2-19 and at wavelengths between 1600 and 1900 cm(-1). The presence of an argon atom is shown to have the effect of reducing the internal energy content of the ions, and for the case of (NO)(2)(+). Ar is the only circumstance under which infrared absorption can be detected for the dimer ion. The trimer ion, (NO)(3)(+), is found to have a very strong absorption feature at similar to 1700 cm(-1), which remains both static and comparatively narrow in subsequent cluster ions containing up to 19 nitric oxide molecules. It is concluded that (NO)(3)(+) forms a stable core in larger clusters and that there is very little additional charge delocalization.