Abstract
A use of a free-electron laser (FEL) as the source of selective vibrational excitation was examined for infrared matrix-assisted laser desorption/ionization time of flight mass spectrometry (IR-MALDI-TOFMS). A polycrystalline mixture of fumaric acid/potassium chloride was exposed to FEL macropulses (15 μs). To make comparison, a pulse TEA-CO2 laser was also employed for the light source of IR-MALDI-TOFMS. In the present study, both the FEL and CO2 lasers were tuned at 10.2 μm. Preliminary results and novel findings are reported. The ability of ionization in the mid-infrared wavelength was evidenced by the mass spectrometric detection of fumaric acid ions. Contrastive absence and presence of low m/z peaks in the TOFMS spectra imply that a softer situation of desorption-ionization was achieved by exposure to the FEL than that to the CO2 laser. A novel ionization process via absorption of a single micropulse was suggested to be possible.
