Temperature programmed desorption mass spectrometer with supersonic molecular beam inlet system

A novel atmospheric temperature programmed desorption-mass spectrometer (TPD-MS) device based on supersonic molecular beams (SMB) is demonstrated. The coupling between SMB and TPD-MS enables one to obtain highly sensitive TPD measurements with very fast time response (less than 1 s), that makes it possible to distinguish between desorptions from energetically neighboring sites. Quantitative adsorption measurements of adsorbing gas and vapors could be easily done. High detection sensitivity 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 monitor simultaneous physical adsorption of nitrogen, oxygen, and water on various sites on carbon fibers at room temperature. (C) 1997 American Institute of Physics.