Department of
Chemistry,
● Spectroscopy and Photochemistry of
Metal-Containing Clusters
● Cluster Models of Metal Ion Solvation and
Coordination
● Protonated Molecular Clusters and Proton
Transfer Dynamics
● Carbocations and Laboratory Studies of Interstellar
Molecules
● Synthesis of Nanocluster Materials
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Dr. Michael A. Duncan Department of Chemistry Office:
706-542-1998 Journal of Physical Chemistry Editorial Office
Fellow, American Physical Society, 2001 Fellow, American Association for the Advancement
of Science, 2004 Alexander von Humboldt Fellow, 2007- |
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August 2008
Front: Katie
Mayo, Biswajit Bandyopadhyay, Mike Duncan, Brian Ticknor, Tim Cheng
Back: Anne
Granville, Zach Reed, Antonio Brathwaite, Gary Douberly, Prosser Carnegie,
Allen Ricks
Research Group:
CURRENT MEMBERS:
Allen Ricks, Graduate Student (aricks@gmail.com)
Collin Dibble, graduate Student
(wollie@uga.edu)
Zach Reed, Graduate Student (zachreed@uga.edu)
Tim Cheng, Graduate Student (timccheng@gmail.com)
Biswajit Bandyopadhyay,
Graduate Student (biswajit@uga.edu)
Scott Akin, undergraduate
research (scakin@uga.edu)
Jeremy Bloomfield,
undergraduate research (jbloom30@uga.edu)
Josh Stein, undergraduate
research (jstein1@uga.edu)
Research Program:
A
major focus of our research program is the synthesis and characterization of
novel atomic and molecular clusters containing metals. These clusters may
consist of only a few atoms of pure metal, mixtures of metals, or metal
compounds (carbides, oxides, etc.), or they may be a metal center with one or
more molecules attached to it. The overall goal is the elucidation of the
chemical bonding between metals and at the metal-molecular interface. The
work is fundamental, but practical implications are easily found in
heterogeneous catalysis, physisorption on metal surfaces, production of
microelectronic materials, metal-ligand bonding, metal ion solvation,
atmospheric meteor ablation chemistry, astrophysics and interstellar dust, and
interactions in metal and semiconductor plasmas. In all projects, the
metal systems are produced in a gas phase/molecular beam environment using
pulsed laser vaporization of metal targets. The resulting clusters and/or
metal complexes are analyzed and size selected using time-of-flight mass
spectrometers. A significant component of the research focuses on the
design and optimization of time-of-flight mass spectrometers. High
resolution spectroscopy measurements are conducted using a variety of tunable
visible, ultraviolet and infrared lasers, using the techniques of laser induced
fluorescence, laser multiphoton ionization, laser multiphoton photodissociation
and laser photoelectron spectroscopy. These studies investigate the
electronic orbital energies, bonding configurations, ionization potentials,
vibrational frequencies, bond energies, bond distances, geometric structures
and photochemical pathways in the clusters. We study neutral clusters as
well as positive and negative ions.
Another major
effort includes the study of proton accommodation and proton transfer dynamics
in molecular networks. Proton transfer
is a critical aspect of biological energy transfer and hydrogen fuel cell
operation, and protonated molecules are active components of atmospheric and
interstellar ion chemistry. We produce
gas phase ions and clusters containing protons bound to inorganic, organic and
organometallic systems and use size-selected infrared spectroscopy to probe the
structures resulting from proton binding.
Systems of recent interest include protonated water clusters,
proton—shared molecular dimers of nitrogen, CO2, acetone,
etc., and protonated organic molecules including protonated acetylene,
ethylene, benzene, naphthalene, etc.
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Research
Areas: |
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Metal Ion Complexes |
Metal-Carbide and Oxide Cages and Nanocrystals |
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Protonated Water Clusters |
Novel Organometallic Clusters |
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Other Protonated Molecular Clusters |
Laser Desorption Mass Spectrometry of Thin Films |
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Carbocations |
Synthesis of Ligand-Coated Nanoparticle Materials
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This is a
photograph of the inside of one of our "source" chambers where
clusters are produced. The sample in this example is a silver rod hanging
down from above that is mounted in a special holder that we built. The
laser comes through the window on the opposite side and hits this rod as it is
rotating. A spray of helium or argon gas flows over the metal rod surface
where the laser hits the rod. The metal-containing cluster molecules
spray out of this (toward the right in this figure) and the center part of this
spray goes through the hole in the "skimmer" (the silver cone-shaped
device mounted on the right wall). This gas then goes into another vacuum
chamber connected to this one where the mass spectrometer is located.
Here is a photograph of one of our beam machines with the
reflectron time-of-flight
mass spectrometer (our lab has three of these
instruments):
Clusters are
produced in the source chamber on the right (see expanded photo above) and then
they flow through the skimmer into the second chamber at left where the mass
spectrometer is loctated. Two pipes come out of this chamber to make the
flight tube for the time-of-flight mass spectrometer. The ions are
reflected down the second pipe in the turning region, which is the can closest
and to the left. This is where the laser excites the ions.