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Laser Ablation/Desorption and Spectroscopy of Biomolecules

This apparatus was developed to study the spectroscopy and photodynamics of non-volatile organic and biological molecules in the gas-phase.

Currently the apparatus makes use a previously built molecular beam apparatus, as schematically represented on the left. It consists of a molecular beam of an inert gas (Ar, He…), in blue on the picture,, created in the first source chamber through the pulsed valve and skimmed into a second chamber containing the extraction region (plates electrically charged) and a linear time-of-flight mass spectrometer.
The sample rod (moiety and dried up solvent) is exposed to the radiation of a pulsed IR laser (1064 nm, red beam),  leading to the heating of the matrice of dry solvent and the indirect evaporation of the molecules of interest.

A second laser ionizes (blue beam), through Resonant MultiPhoton Ionization (REMPI) the molecules that are then accelerated by the electric field towards the detector. By recording the gated (in time, therefore mass-selected) signal from the MultiChannel Plates detector, one can record the REMPI spectrum of the entity studied.

A third laser (green beam) can be slightly delayed in time or focalized above the ionization laser in order to proceed to Resonant MultiPhoton Dissociation (RMPD) of the ion previously created. By recording the signal arising from the fragment one gets information on the absorption and dissociation channels of the ionic species.

by D. Rolland, J.W. Hepburn

Presented at: International Symposium on Molecular Spectroscopy 57th Meeting - Ohio, USA - June 2002