High excitation ISM and gas
  An overview is given of ISO results on regions of high excitation ISM and gas, i.e. HII regions, the Galactic Centre and Supernovae Remnants. IR emission due to fine-structure lines, molecular hydrogen, silicates, polycyclic aromatic hydrocarbons and dust are summarised, their diagnostic capabilities illustrated and their implications highlighted. 
E. Peeters, N.L. Martin-Hernandez, N.J. Rodriguez-Fernandez, A.G.G.M.   Tielens