Magic-angle thermal desorption mass spectroscopy

摘要: Abstract Accurate quantitative measurements of desorption rates or adsorbate coverages in thermal mass spectroscopy (TDS) using line-of-sight spectrometers are hindered by the fact that angular distributions flux can vary widely from desorbate to desorbate, ranging cos1o cos9 o for most species studied date (o = polar angle surface normal). These differences easily lead errors exceeding 400% measuring relative different species. We show here that, placing spectrometer's ion source entrance aperture at a “magic-angle” mthese be reduced less than 26% maximum deviation (or ± 7% standard deviation). Depending upon sample-to-detector distance, m varies ~ 42° 34°. It is recommended TDS experiments performed this improvement accuracy coverage rate measurements.