Abstract
This review covers spectroscopic results obtained with ISO on molecular and atomic line emission from the circumstellar envelopes of oxygen-rich AGB stars and post-AGB objects and from cool supergiant stars. As well as the SWS detection of the 4.27-μm CO2 band in absorption and emission from cool star envelopes, several new emission bands which have been detected in SWS spectra between 13.9 and 16.2 μm have been identified with CO2 bands. Strong H2O line emission has been observed in the LWS and SWS spectra of high mass loss rate O-rich AGB and M supergiant stars, confirming the predicted importance of this molecule as a coolant in their outflows. The proposed infrared radiative pump mechanism for circumstellar OH masers has been directly confirmed for the first time via measurements for several stars of the OH infrared pumping lines between 34.6 μm and 163 μm. Water vapour emission lines are not present in the spectra of O-rich post-AGB objects, having been replaced by broad emission features at 43 and 62 μm due to crystalline water ice that has condensed in the very cool outflows.
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