TEMPERATURE-PROGRAMMED DESORPTION MASS-SPECTROMETER WITH SUPERSONIC MOLECULAR-BEAM INLET SYSTEM

A novel atmospheric temperature programmed desorption-mass spectromete r (TPD-MS) device based on supersonic molecular beams (SMB) is demonst rated. The coupling between SMB and TPD-MS enables one to obtain highl y sensitive TPD measurements with very fast time response (less than 1 s), that makes it possible to distinguish between desorptions from en ergetically neighboring sites. Quantitative adsorption measurements of adsorbing gas and vapors could be easily done. High detection sensiti vity of 4 ng/s for H2O16 and 100 pg/s for H2O18 is achieved. The high sensitivity TPD measurements are demonstrated by the ability to monito r simultaneous physical adsorption of nitrogen, oxygen, and water on v arious sites on carbon fibers at room temperature. (C) 1997 American I nstitute of Physics.