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High performance photolysis TOFMS

Photolysis II

Kore has developed a second-generation higher performance system for gas phase kinetics studies. One instrument has been delivered to the University of Bordeaux and a second to University of Leeds, who already own an older Kore system. Typically the reactions take place in a flow tube and are started with a pulsed laser. The transient that follows may be studied by examining ions already present, or by ionising using a second laser or an electron impact source. Using a time-of-flight mass spectrometer allows all species to be followed at once. Both analogue and digital outputs are available, the appropriate choice depending on the repetition rate available from the laser(s). For example, ion counting in raw list mode, over many nominally identical transients to build up good statistics, allows great flexibility in the subsequent retrospective data processing.

Novel ion-collection optics, placed in line with the gas entry, allow a differential pumping aperture to be sited within the spectrometer itself, close to the pulsed extraction region. This allows the spectrometer to tolerate a relatively high pressure in the source region without heroic pumping measures. The pumping system used in this example, consists of 2 240l/s turbomolecular pumps backed by a scroll pump.

There can be up to 4 pressure regions:

The flow tube where the chemical reactions take place typically 1 bar
A roughing chamber, pumped by the scroll pump typically 0.1 to 1 mbar
The ion extraction chamber, pumped by the first turbo typically around 10-4 mbar
The spectrometer, or at any rate the bulk of it, including the detector and pumped by the second turbo typically around 10-6 mbar


System schematic

10:29 15/07/2013

Kore Technology Limited 2013