Knowledge Bank

In the last decade, IR observations of dense interstellar clouds have been used to detect both gas phase molecules and molecules in the mantles of dust particles. While the gas phase molecules can be studied via high resolution spectroscopic techniques, the mantle material can only be studied via low resolution. Nevertheless, the low resolution spectral features can be assigned with varying degrees of certainty. We have recently undertaken model calculations of both the gas phase and grain surface chemistry of dense interstellar clouds with a goal of predicting molecular abundances in grain $mantles1$. The calculated mantle abundances compare favorably with those determined from selected low resolution observations of interstellar clouds and demonstrate that both gas phase syntheses followed by adsorption onto the dust particles and syntheses occuring on grain surfaces contribute to mantle molecular abundance. New results in which non-thermal desorption mechanisms are included in the model will be presented.