Nonionic surfactant adsorption layers are investigated by applying 2H NMR to selectively deuterated dodecyl penta(ethylene oxide), C12E5, adsorbed on colloidal silica. Results for surface aggregates are compared with different types of bulk aggregates such as micelles, which show isotropically averaged Lorentzian line shapes, and with liquid crystalline phases, which show a Fake pattern spectrum. Surface aggregate spectra are isotropically averaged, with relaxation rates R-2 of several kilohertz, indicating a slow motion correlation time of the order of microseconds. Possible mechanisms of isotropic averaging of the quadrupolar interaction in surface aggregates and the implications for the structural arrangement are discussed. To compare results from solid and liquid spectra, we introduce the concept of a relative order parameter profile S-rel of the C-2H bond. Adsorption layers can thus be directly compared with micelles, and with lamellar and hexagonal phases with respect to their internal mobility. An increase of S-rel with distance of the 2H label position from the headgroup is found for all bulk aggregate types, with the slope depending on aggregate: curvature. The result is interpreted in terms of packing constraints and chain interaction. Comparison of the results for surface aggregates with these profiles gives an indication of their curvature and structure. S-rel profiles of adsorption samples do not depend on water content or surface coverage. All results, that is, the structural implications from S-rel profiles as well as time scales of surfactant motional modes, are consistent with the formation of large anisotropic surface aggregates, which can be described as a disrupted bilayer. The motions causing isotropic averaging probably are lateral diffusion in combination with surfactant exchange processes.