Thermal Desorption Fourier Transform Mass Spectrometry

As the sample is heated, species desorb from the front face and expand into the FTMS cell. A 70eV electron beam is pulsed down the center of the cell and ionizes some the neutrals. As the remaining neutrals are pumped away, the ions are trapped due to the presence of magnetic and electric fields. The ions follow circular paths in the magnetic field and are excited into larger orbits (cyclotron motion). The image current induced on opposing cell plates by the cycling ions is detected and the signal is amplified, digitized and Fourier transformed to yield a complete mass spectrum in a single scan.

Laser-Induced Thermal Desorption - Fourier Transform Mass Spectrometry (LITD-FTMS)

A Nd:YAG laser (1064 nm, 5 ns pulse, 8 mJ/pulse) is focussed on a 1mm diameter spot on the sample. Species desorb from under the laser shot and some of the neutrals are ionized by a 70eV electron beam. As the remaining neutrals are pumped away, the ions are trapped due to the presence of magnetic and electric fields. The ions follow circular paths in the magnetic field and are excited into larger orbits (cyclotron motion). The image current induced on opposing cell plates by the cycling ions is detected and the signal is amplified, digitized, and Fourier transformed to yield a complete mass spectrum in a single scan.