The Raman-active vibron modes of solid nitrogen have been investigated by coherent anti-Stokes Raman scattering (CARS) spectroscopy to 22 GPa at room temperature. Frequencies and linewidths were measured with an accuracy of 0.1 to 0.2 cm(-1). From the pressure dependence of the linewidths a dynamical model for the transitions between the delta, delta (loc), and epsilon phases has been developed. These phase transitions are characterized by different degrees of ordering of the N-2 molecules. The processes can be described by an increase in the orientational order with increasing pressure and a decrease in number in the rotational degrees of freedom at the phase transitions coupled with changes in crystal structure. A structural model for the delta (loc) phase is given, in which the delta-delta (loc)-epsilon transition sequence arises from a group/subgroup relationship and can therefore be considered ferroelastic in nature. Sample annealing was found to have a significant effect on the results.