Knudsen effusion mass spectrometry instrument

Knudsen effusion mass spectrometry is used to measure the composition of the effusing beam (including the composition of the sample investigated, fragments or newly formed species) and in particular to determine the thermochemical data. The instrumentation is briefly described in Section 5.2.10.137... 

Hastie [131] coupled for the first time a quadrupole mass spectrometer with a Knudsen cell. One of the quadrupole mass spectrometer - Knudsen cell systems used at our laboratory is shown in Fig. 4. The system has been developed to study small alkali metal clusters under equilibrium conditions (see Sect. 3.2). Broad-band photoionization by a 1 kW Hg/Xe lamp is used for the first time in Knudsen effusion mass spectrometry to reduce fragmentation. Other quadrupole mass spectrometer - Knudsen cell systems have for example been developed by Hilpert [132, 133], Fraser and Rammensee [134], Plante [135], Ono et al. [136], Kematick et al. [137], and Edwards et al. [138]. Cryogenic pumping is used in the device by Hilpert to reduce mercury background ion intensities for the study of amalgams [132], The instruments described in Refs. 134,135 use a chopper to modulate the molecular beam from the Knudsen cell. Interfering background ion intensities can, thereby, be subtracted. The apparatus developed by the authors of Refs. 137, 138 renders possible the simultaneous application of Knudsen effusion mass spectrometry and the mass-... 

The potential of Knudsen effusion mass spectrometry for the study of ion-molecule and ion-ion reactions in the Knudsen cell is discussed and the instrumentation described in the recent review article by Sidorov et al. [572]. In this section the results determined for halides by studying equilibria involving negative ions are reviewed as an example for this interesting variant of the method. 

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