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In
addition to a full complement of laboratory apparatus necessary
for synthesis and characterization (UV-visible spectrometers, FTIR,
electrochemical analyzer, HPLC etc..) we have several state of the
art kinetics measurement systems. The equipment in our group allows
for kinetics measurements to be made in time regimes from picoseconds
to days. Kinetics measurements can be measured by rapid mixing in
a stopped-flow spectrometer (Applied Photophysics model SX18-MV).
The stopped flow instrument has both absorbance and fluorescence
detection as well as sequential mixing capabilities. This instrument
allows analysis of chemical reactions occurring in milliseconds
or longer. For faster reactions we use one of several laser flash
photolysis systems described following the links below.
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The
Stopped-flow Spectrometer allows fast chemical reactions initiated by
stopped-flow and sequential mixing stopped-flow to be following using
absorption detection. Click here to find out
about the set-up at the Ford Laboratory.
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All
of the flash photolysis apparati used in this laboratory are modifications
of the classical flash photolysis apparatus described by Norrish
and Porter. The general methodology for these experiments requires
that a sample be pumped or excited (laser excitation in this laboratory)
then the reactive intermediates are probed at the appropriate wavelength.
There are two strategies used in this laboratory to collect the
data. The first is to monitor a single wavelength of probe light
versus time. In order to get a transient difference spectrum, data
must be collected at many different wavelengths. The second, available
only in the optical region, uses a charged coupled device (CCD)
detector to collect the entire spectrum following each laser pulse.
However, to obtain temporal information, one must collect data at
different time delays. These two techniques are complementary to
each other. Typically the transient difference spectra is collected
first (CCD) in order to decide which wavelength gives the greatest
signal. The temporal response is then collected (PMT) at the particular
wavelengths of interest.
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