The method of Se isotope substitution with inelastic neutron scattering will be used to measure the partial VDOS for As2Se3 glass. This is a prototypical network forming material, part of a family that provide the basis of glasses with important infrared transmitting and other optical properties. The predominant structural motif in this glass is the pyramidal AsSe3 unit, in contrast with many other network forming materials (e.g. GeSe2, GeO2, SiO2) which are constructed from corner and/or edge sharing tetrahedra. The results will therefore provide insight into the dynamics of networks with contrasting connectivities. They will also be used in the development of realistic first principles molecular dynamics models for As2Se3 glass. The experiments will make full use of the attributes of the MERLIN spectrometer.