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, Fritz Haber
Institute, |
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August 2009
Left to right:
Scott Hasbrouck, Biswajit Bandyopadhyay, Allen Ricks, Collin Dibble, Shaun
Ard, Antonio Brathwaite, Mike Duncan,
Tim Cheng, Dale Autry, Zach Reed
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)
Antonio Brathwaite, Graduate
Student (abrathwa@uga.edu)
Jonathan Mosely, Graduate
Student (jdmosley@uga.edu)
Shaun Ard, Postdoctoral
Research Associate (sard@uga.edu)
Areatha Ketch, Postdoctoral
Research Associate (areatha@gmail.com)
Jakie Chao, Undergraduate
Student (chaokuot@uga.edu)
Dale
Autry, Visiting high school teacher (autryd@clarke.k12.ga.us)
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, multiphoton ionization and photodissociation 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, CO, 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. 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
it. 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 an adjacent vacuum chamber 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.