This solicited ISO open time proposal aims at building a
complementary data base of ISO spectroscopic and imaging
observations to study the thermal balance of
dense and warm interstellar matter and the interaction of UV photons with
molecular gas and dust in Photo-Dissociation Regions (PDRs).
This proposal follows up the unexpected detection of the S(3) and S(5)
v=0-0 lines of H2 in CVF observations of NGC 7023, M17 and two
Ophiuchus PDRs. We propose to obtain (1) SWS and LWS spectra at
positions selected on the basic of ISOCAM images
and (2) CVF H2 images of targets already observed with the spectrometers.