A multipurpose quadrupole mass spectrometer detector for surface kinetic and absolute surface coverage measurements

A multipurpose mass spectrometer detector has been constructed for studies of adsorption and desorption from single‐crystal surfaces in an ultrahigh vacuum system. The detector may be used for studies of the kinetics of adsorption on single crystals using collimated and calibrated molecular‐beam dosers, as well as the direct measurement of the absolute sticking probability as a function of the absolute surface coverage. In addition, using a small sampling aperture for line‐of‐sight desorption procedures, it is possible to achieve high sensitivity for the detection of gaseous desorption products as well as condensible products. In the direct line‐of‐sight detection mode of operation, a desorbing free radical species has been detected. Normally, mass spectrometers used in ultrahigh vacuum systems are not able to be employed for the combination of purposes addressed by this instrument.