Employing a quartz crystal microbalance and a quadrupole mass spectrometer in a vacuum chamber, thermogravimetric analyses (TGA) and mass spectrometer analyses have been performed at low temperature on depositions of ammonia, acetone, methanol, toluene, isopropyl alcohol, water, para-xylene, and selected combinations. Deposition of a single species yielded a TGA curve characteristic of a pure substance. Homogeneous binary mixtures, like methanol and water, exhibited a desorption curve which included structure that was intermediate to that observed for pure materials. Sequential layering of one material on top of another also altered the TGA response, and the TGA curve shape was found to be a function of top-layer thickness for the water-on-methanol system. Backfilling the chamber with nitrogen or argon at a pressure of 1 Torr shifted the sublimation temperature of water about 20 K higher.
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