MATRIX ISOLATION FOURIER TRANSFORM-INFRARED SPECTROMETRY OF LASER-DESORBED SPECIES/

Initial results are presented for a novel experimental arrangement whi ch allows the successful study of laser-desorbed neutral species under matrix isolation conditions. In the current work, a pulsed carbon dio xide laser (10.6 pm) is employed for laser desorption. With the combin ation of a previously described cryogenic trapping technique with coax ial matrix isolation gas (xenon or argon) introduction, laser-desorbed neutrals have been matrix isolated and their Fourier transform infrar ed spectra recorded. Two different cinnamic acid derivatives (p-coumar ic acid and sinapinic acid) typically employed for matrix-assisted las er ionization (MALDI) mass spectrometry were utilized to demonstrate t his new technique. Experimental conditions were determined for optimal matrix isolation of the laser-desorbed species. Two different desorpt ion geometries were examined with respect to their effectiveness for m atrix isolation of desorbed neutrals. A covalent dimer of p-coumaric a cid produced in an external UV photoreactor and thought to be a possib le photoreaction product in UV MALDI was studied by this technique. Th ermal degradation of this dimer is shown to occur above threshold irra diance for laser desorption.