C-13 NMR T-1, NOE, and T-1 rho Were measured for two unentangled polyethylene melts (C44H90 and M-w = 2150 g/mol) at 5, 25, and 75 MHz C-13 Larmor frequency from the melting points up to 260 degrees C. The data were fit with a model composed of a fast segmental relaxation and a long time tail described by Rouse modes. The fitting parameters are consistent with MD computer simulations on similar systems and independent experiments such as viscosity and self-diffusion coefficient measurements. Polyethylene is an unusual polymer in that it has a very pronounced long time tail in the C-H vector correlation function. This long time tail makes this experiment a sensitive tool with which to characterize the global dynamics of polyethylene melts. Rouse modes, with corrections suggested from MD simulation, were found to be an adequate description of the global dynamics in this molecular weight range. The activation energy for the conformational dynamics was found to be 4 kcal/mol, which is significantly less than the flow activation energy. Therefore, in contrast to some other well-studied examples, conformational transitions are not the fundamental motions for now in polyethylene. MD computer simulations of C44H90 [Smith et al. Macromolecules 1995, 28, 5897] using an explicit atom model closely reproduce the experimental data.