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Research in our group is focused on gas-phase ion spectroscopy, with a particular emphasis on problems related to reactive intermediates and cluster ions. Our experiments require careful ion synthesis, followed by mass selection in a mass spectrometer. We learn about the ion properties by 1) using infrared or UV lasers to detach electrons in photoelectron imaging or 2) electronic or vibrational spectroscopy by photodissociation.
1. Reactive intermediates. Radicals, carbenes and other exotic reactive intermediates are difficult to observe experimentally due to their highly reactive nature, whereas studies of these molecules are vital for verifying and understanding reaction mechanisms. Because these molecules all have at least one partially filled orbital, they readily add extra electrons to form stable negative ions. We exploit this property by generating anion analogs of reactive intermediates and then remove the electron by laser excitation. For these studies, photoelectron imaging is especially powerful because electron detachment yields detailed information on the electronic states and orbital symmetries of the neutral intermediates. One of our major goals in this field is to study perturbation effects on electronic structure arising from heteroatom substitution at various locations within a molecular framework.
2. Cluster ions. Small, size-selected, cluster ions are ideal model systems for studying solvent-solute interactions under carefully controlled conditions. In this experiment we learn about microsolvation, systems that are best described as heterogeneous nanodroplets. Clusters are important because they provide the link between isolated gaseous ions and their solvated (bulk) counterparts. We identify vibrations in small clusters, which are characteristic of the spatial arrangement of atoms. These vibrational frequencies may shift, change intensity, disappear, or new modes might appear as the degree of solvation increases and the structure adopts a configuration similar to that found in the condensed phase. These spectral fingerprints can be used to determine the local solvent-solute structure in solution.
“The C-H Bond Dissociation Energy of Malononitrile.” Goebbert, D. J.; Velarde, L.; Khuseynov, D.; Sanov, A. J. Phys. Chem. Lett. 1 792-795 (2010).
“Photoelectron Imaging of Cyanovinylidene and Cyanoacetylene Anions.” Goebbert, D. J.; Khuseynov, D.; Sanov, A. J. Phys. Chem. A 114 2259-2256 (2010).
“Infrared Spectroscopy of Hydrated Bicarbonate Anion Clusters: HCO3-(H2O)1-10.” Garand, E.; Wende, T.; Goebbert, D. J.; Bergmann, R.; Meijer, G.; Neumark, D. M.; Asmis, K. R. J. Am. Chem. Soc. 132 849-856 (2010).
“Laboratory observation of the valence anion of cyanoacetylene, a possible precursor for negative ions in space.” Goebbert, D. J.; Khuseynov, D.; Sanov, A. J. Chem. Phys. 131 161102 (2009)
“Photodetachment, photofragmentation and fragment autodetachment of [O2n(H2O)m]- clusters, Core-anion structures and fragment energy partitioning.” Goebbert, D. J.; Sanov, A. J. Chem. Phys. 131 104309 (2009)
“On the Low-Lying Electronic States of the Oxyallyl Diradical.” Ichino, T.; Villano, S. M.; Gianola, A. J.; Goebbert, D. J.; Velarde, L.; Sanov, A.; Blanksby, S. J.; Zhou, X.; Borden, W. T.; Lineberger, W. C. Angew. Chemie Int. Ed. Engl. 48 8509-8511 (2009)
“Infrared Spectroscopy of Solvated NO3-(H2O)n, n = 1 – 6.” Goebbert, D. J.; Wende, T.; Bergmann, R.; Garand, E.; Neumark, D.; Meijer, G.; Asmis, K. R. J. Phys. Chem, A 113 7584-7592 (2009)
“Messenger-tagging Electrosprayed Ions: Vibrational Spectroscopy of Suberate Dianions.” Goebbert, D.; Wende, T.; Meijer, G.; Asmis, K. R. J. Phys. Chem. A 113, 5874-5880 (2009)
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