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High Resolution Spectroscopy and Dynamics of Transient
Species
Trevor J. Sears, Gas Phase Molecular Dynamics
Group The
structure and behavior of chemically reactive intermediates control the
outcome of all chemistry. In this research, we develop and use high
resolution spectroscopic techniques to investigate the structure and
properties of intermediate species involved in elementary reactions
relevant to combustion chemistry, and to the processes occurring in
catalysis at the gas solid interface. The experimental measurements are
complemented by theoretical and computational methods with the combined
aim of characterizing the intra- and inter-molecular potential energy
functions governing the species' reactivity. The work leads to a detailed
understanding of the molecular-level changes that occur in these
complicated processes and provides the basis for testing and refining the,
necessarily simplified, models for them. Ultimately, the research leads
to the prediction of improved ways for achieving desired chemical
transformations, minimization of pathways leading to unwanted or polluting
products, and to the more efficient use of fossil fuel or other
non-renewable resources.
In our group, laser absorption spectroscopy has been
the experimental tool of choice since it is a linear technique, lineshape
functions are well understood, and therefore measurements are easily
related to species concentrations and energies. Some years ago we
developed a method to increase the sensitivity of the technique by
frequency modulating the laser output and using heterodyne detection. When
applied to the study of transient species, the absorption sensitivity in
the experiment can routinely approach the theoretical quantum noise limit
for the observation time window. By changing the length of the observation
time window, absorption sensitivity can be traded for time resolution.
Using single frequency c.w. lasers, the technique has been applied to
measure the spectra of free radical and other transient species and for
dynamical and kinetic measurements involving short-lived molecules in
combustion and plasma environments.
Recent
work has focussed on the spectroscopy and dynamics of methylene and
related carbenes, and on spectroscopy of transition-metal-containing
radicals. Details can be found in the papers listed in the publication
list below, and elsewhere on this site.
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