We propose to measure the powder-averaged spin excitation spectrum of LiFeAs, a new member of the ferropnictide family of superconductors. This compound is special because it is stoichiometric and therefore not chemically doped, and yet it is a superconductor below Tc ~ 18K. Our aim is to establish to what extent the spin dynamics in this material resembles the non-superconducting parent phases and to what extent it resembles the extrinsically doped superconductors. There are two objectives. First we will measure the bandwidth of the spin excitation spectrum and compare the results with a model developed for the stoichiometric non-superconducting parent phases like BaFe2As2. Second we will search for the existence of a resonance-like excitation below Tc, as observed in superconducting (Ba1-xKx)Fe2As2.