INFRARED SPECTROPHOTOMETRY OF M17 WITH ISOCAM

We report spectrophotometric observations of the H II region/neutral m edium interface in M 17 obtained with the ISOCAM Circular Variable Fil ter (CVF) in the spectral range 5.15 to 16.5 mu m. The lines of singly -ionized species come mainly from the clumpy ''neutral'' interface, wh ile the H II region dominates the line emission by higher-ionization s pecies. The emission in the Unidentified Infrared Bands (UIBs) comes f rom the molecular cloud and the interface and extends into the H II re gion. In the regions where the radiation field is larger than about 10 (4) times the standard interstellar one, the continuum is dominated by the emission of very small grains which are bigger than those respons ible for the UIBs.