Johnson, Christopher - Stony Brook University

个人简介

B.S., Butler University, 2005 Ph.D., University of California, San Diego, 2011 NSF Postdoctoral Fellow, Yale University, 2011-2013 Postdoctoral Associate, Yale University, 2013-2014

研究领域

Multiplexing laser spectroscopy and mass spectrometry to address challenges in energy and the environment We are interested in resolving the molecular-level mechanisms underlying a broad range of chemical phenomena from new particle formation in the atmosphere to catalytic activity in solution and biofuel combustion, as well as understanding the active role that solvent (particularly water) plays in these reactions. Our contribution to these fields involves identifying and characterizing the reactive intermediates governing these chemical processes, which are often too short lived or in too low concentration to be observed using typical chemical analysis techniques. By harnessing and continuing to push forward new advances in mass spectrometry and ion trapping, we can create unique instruments that, in a very general way, isolate intermediates of interest directly from solution, chemically manipulate them through controlled gas-phase reactions, then interrogate them using a powerful and ever-expanding suite of spectroscopic (electronic and vibrational) and thermochemical techniques. Please visit the group site for more information on how these experiments are carried out. Atmospheric Chemistry New particle formation (the generation of particles directly from atmospheric vapors) is a nearly ubiquitous process in the ambient atmosphere, but it remains one of the most poorly understood. This is largely due to a lack of understanding of the critical chemical interactions taking place in these highly heterogeneous systems at the few-molecule to cluster level, or the sub-nanometer to nanometer range. We intend to fill this gap in understanding by generating seed clusters of 3-10 molecules, reacting them in a controlled way with vapors expected to play a role in particle growth, and using vibrational spectroscopy and thermochemistry to identify and characterize the critical intermolecular interactions responsible for controlling particle growth rates. Catalysis We are interested in characterizing catalysts in the act of catalysis – specifically isolating the active species and trapping the active catalyst-reactant complex. This information can help to rigorously validate the proposed cycles for many catalysts, fine tuning our understanding of the overall mechanisms. We are also interested in what, if any, role individual solvent molecules may play in these processes, whether they be structural in nature or active participants in proton transfer, etc. Fundamentals of Spectroscopy and Intermolecular Interactions Tying together all of our interests are open questions in physical chemistry regarding the non-trivial ways in which molecules interact, and the spectroscopic ramifications of these interactions. Ultimately, we find that in order to properly analyze the results in the projects above, we must first stop to understand some new phenomenon upon which we stumble. This interplay between fundamentals and applications always keeps this work exciting!

近期论文

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Johnson, C. J., Dzugan, L. C., Wolk, A. B., Leavitt, C. M., Fournier, J. A., McCoy, A. B., and Johnson, M. A., "Microhydration of Contact Ion Pairs in M2+OH–n=1-5 (M=Mg, Ca) Clusters: Spectral Manifestations of a Mobile Proton Defect in the First Hydration Shell," J. Phys. Chem. A, DOI: 10.1021/jp504139j. Johnson, C. J., Wolk, A. B., Fournier, J. A., Sullivan, E. N., Weddle, G. H., and Johnson, M. A., "Communication: He-tagged vibrational spectra of the SarGlyH+ and H+(H2O)2,3 ions: Quantifying tag effects in cryogenic ion vibrational predissociation (CIVP) spectroscopy," J. Chem. Phys., 140, 221101 (2014). Fournier, J. A., Johnson, C. J., Wolke, C. T, Weddle, G. H., Wolk, A. B., and Johnson, M. A., "Vibrational spectral signature of the proton defect in the three-dimensional H+(H2O)21 cluster," Science, 344, 1009 (2014). Ingram, A. J., Wolk, A. B., Flender, C., Zhang, J., Johnson, C. J., Hintermair, U., Crabtree, R. H., Johnson, M. A., and Zare, R. N., "Modes of activation for organometallic iridium complexes involved in catalytic water and CH oxidation," Inorg. Chem., 53, 423 (2014). (cover article Jan. 6, 2014) Johnson, C. J., Fournier, J. A., Wolke, C. T., and Johnson, M. A., "Ionic liquids from the bottom up: Local assembly motifs in [EMIM][BF4] through cryogenic ion spectroscopy," J. Chem. Phys., 139, 224305 (2013). Leavitt, C. M., DeBlase, A. F., Johnson, C. J., van Stipdonk, M., McCoy, A. B., and Johnson, M. A., "Hiding in Plain Sight: Unmasking the Diffuse Spectral Signatures of the Protonated N-Terminus in Isolated Dipeptides Cooled in a Cryogenic Ion Trap," J. Phys. Chem. Lett., 4, 3450 (2013). Johnson, C. J. and Johnson, M. A., "Vibrational Spectra and Fragmentation Pathways of Size-Selected, D2-Tagged Ammonium/Methylammonium Bisulfate Clusters," J. Phys. Chem. A, 117, 13265 (2013) Johnson, C. J., Harding, M. E., Poad, B. L. J., Stanton, J. F., and Continetti, R. E., "Electron Affinities, Well Depths, and Vibrational Spectroscopy of cis- and trans-HOCO," J. Am. Chem. Soc., 133, 19606 (2011). Johnson, C. J., Shen, B. B., Poad, B. L. J., and Continetti, R. E., "Photoelectron-photofragment coincidence spectroscopy in a cryogenically cooled electrostatic ion beam trap," Rev. Sci. Instrum., 82, 105105 (2011). Johnson, C. J., Poad, B. L. J., Shen, B. B. and Continetti, R. E., "Communication: New insight into the barrier governing CO2 formation from OH + CO," J. Chem. Phys. 134, 171106 (2011). Poad, B. L. J., Johnson, C. J., and Continetti, R. E., "Photoelectron-photofragment coincidence studies of NO−-X clusters (X=H2O, CD4)," Faraday Discussions 150, 481 (2011). Johnson, C. J. and Continetti, R. E., "Dissociative photodetachment studies of cooled HOCO- anions revealing dissociation below the barrier to H + CO2," J. Phys. Chem. Lett. 1, 1895 (2010