Electronic excitations in lithium ammonia

We have carried out inelastic X-ray scattering measurements of the plasmon in liquid lithium ammonia solutions with the composition Li(NH3)(4). We find a well-defined plasmon at an energy loss of approximately 2 eV, which displays a positive dispersion in momentum transfer q. The dispersion is reduced from that predicted by the random phase approximation (RPA), but is still larger than is predicted by some local field correction models. (C) 2000 Elsevier Science Ltd. All rights reserved.