Contents of: VI/111/./abstract/RLAUREIJ_RJLR_1_A.abs

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 Interstellar neutral clouds, located close to newly born HII regions,
 are exposed to the ionizing radiation of the central star, and
 the expanding ionized gas drives a strong shock front into them. An
 ionized boundary layer is formed which transforms ultraviolet photons
 to the optical regime, making this layer to be observable as a bright
 rim at the surface of the clouds. Little is known on the properties of
 dust grains processed by the shock front, although this information
 is required by calculations of thermal balance of ionized regions as
 well as by attempts which use infrared emission as diagnostic tool for
 the derivation of physical parameters of the emitting region.

 We propose a comparative study of dust properties in 3 bright rims
 located at different distances from the central star of the HII region
 IC1396. They are excited by the same star but exposed to different
 velocity shocks, so their study may reveal the dependence of infrared
 spectral distribution on shock velocity, and may answer whether
 infrared data could be used for the derivation of shock velocity. The
 results also may help to interpret the variations in dust size
 distribution found by IRAS in interstellar clouds.

 We derive properties such as temperature and size distribution of dust
 particles in interstellar bright rims on the basis of their spectral
 distribution. This goal requires the observation of the infrared
 spectrum of the rims in the whole infrared regime and, in addition,
 observation of the spectral lines emitted by macromolecules (PAHs).
 The existing IRAS data base consists of data taken at 12, 25, 60, and
 100 micron, and contains little information on both the very small and
 very cold dust component. ISO is perfectly suited for this kind of
 observations because of its observing capacity in the 3 to 240 micron
 wavelength range, and the filter set fitted for macromolecule features.

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