Many chemical processes produce species which emit IR radiation. Such emission is weak, but can be wavelength resolved with high sensitivity by using the advantages of Fourier Transform methods. We utilise a time resolved variant of this technique (TR-FTIR), so that spectral changes in the course of a reaction can be followed with microsecond resolution. This can be used for a variety of studies on product vibrational state distributions in photochemistry and chemical reactions, on product branching ratios and kinetics of reactions of combustion and atmospheric interest, and on energy transfer processes.

We have a commercial interferometer (Bruker IFS 66/S) capable of operating in step-scan mode in order to acquire time resolved spectra. This is used in conjunction with a vacuum system with Welsh cell collection optics to study IR emission from species dissociated by an excimer laser. Recent work has focused on:

  • The 193 nm photolysis of NO 2 , revealing a bimodal nascent NO vibrational distribution.
  • Reactions of O( 1 D) with atmospherically important species such as simple hydrocarbons and fluorocarbons.
  • Vibrational quenching of NO(? = 1 ? 16) by atmospheric species.

Current work is focused on the set-up of a cavity-enhanced absorption cell to be used in conjunction with the interferometer, with the aim of developing a new sensitive detection technique.