SOLID CO2 TOWARDS NGC7538 IRS1

We report the observation of the young infrared source NGC7538 IRS1 wi th the Short Wavelength Spectrometer (SWS) onboard the ISO satellite i n the 2.4-45 mu m range. The spectrum exhibits several absorption feat ures due to silicates and to molecular species frozen on the refractor y dust. In particular the stretching and bending mode of solid CO2 hav e been identified. In this paper we present a comparison of the observ ed absorption band at about 15.1 mu m (660 cm(-1)) attributed to the b ending mode of solid CO2 with laboratory spectra of ion irradiated ice mixtures.