Time-Resolved Fourier Transform Spectroscopy

For reactions producing vibrationally or electronically excited molecules, emission-based time-resolved Fourier transform spectroscopy (TR-FTS) can be a fruitful way to study the reaction rate, product state, and branching ratios of elementary combustion reactions. Time-resolved Fourier transform spectroscopy (TR-FTS) yields measurements of thermal rate coefficients as a function of temperature and pressure, and its inherently multiplexed nature makes it possible to simultaneously measure product branching ratios, internal energy distributions, energy transfer, and spectroscopy of radical intermediates. Together with total rate coefficients, this additional information provides further constraints upon and insights into the potential energy surfaces that control chemical reactivity.

While there has been great progress in gas phase emission-based TR-FTS, David Osborn is also developing absorption techniques because they are more general than emission methods and are not complicated by fluorescence lifetime effects or predissociation. Another thrust of this program is toward kinetic measurements of larger molecules. The development of absorption-based TR-FTS in the mid-infrared "fingerprint" region will enable reactivity studies of larger hydrocarbons (C₃—C₆) found in practical fuels.

During the last year, the group designed and constructed the new Kinetics and Mechanisms Laboratory in Phase II of the CRF. The time-resolved Fourier transform spectrometer is now operational. Electronic emission from the fragmentation of NH₃ was studied to troubleshoot the system.