DUAL CRYOGENIC ION TRAP SPECTROMETER FOR SPECTROSCOPY OF COLD ION-MOLECULES COMPLEXES

Ion traps provide a great environment for carrying out controlled ion-neutral molecular reactions. They not only allow for low-temperature chemistry but also for the formation of weakly-bound clusters suitable for vibrational predissociation spectroscopy. Here we present a novel dual cryogenic ion trap spectrometer which combines both capabilities. The first ion trap allows for temperature controlled (77-300K) ion-neutral reaction and clustering, while the second ion trap further thermalize (10K) the reacted complexes and prepare them for subsequent infrared vibrational predissociation characterization._x000d_ _x000d_ Our studies show that at 80K, large solvated clusters with more than 50 water molecules can be formed around almost any ions inside the first ion trap. This opens the door for studies of peptide structures as a function of solvation. Preliminary data on the microsolvation of model protonated (Gly)$_{n}$ peptides will be presented. One complication in these studies is the presence of multiple conformations and resulting spectral congestion which hinders the spectral analysis. We approached this issue in two different ways. First, taking advantage of temperature dependent H-D exchange, we formed D$_{2}$O solvated all H peptides and thus separated the spectral signatures of the solvent and solute into two different regions. Second, implementation of a simplified IR-IR double resonance scheme allowed us to efficiently extract conformation-specific spectrum from complex mixture of isobaric molecules. The combination of these two approaches opens the possibility of studying very complex clusters with high structural specificity. _x000d