We propose a detailed investigation of the properties of the dust
emission features associated with Polycyclic Aromatic Hydrocarbons as
seen towards many galactic and extragalactic sources.  This study will
concentrate on the PAH features in the 5 to 12 micron range as observed
towards galactic HII regions.  Earlier low resloution (R~250) SWS AOT1
observations show very clear variations in the PAH spectrum in this
wavelength range.  Theoretical calulations indicate strong dependence of
the details in the PAH spectrum depending on composition of the emitting
material.  Comparing the proposed high resolution observations to these
models will allow us a a detailed investigation into the composition of
the PAHs and their ionisation state.