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Tunable Far Infrared (TuFIR) Spectroscopy


Cambridge Sum Frequency Spectroscopy



Spectroscopy is the physical science which studies interactions between electromagnetic radiation, (i.e. light), and matter (e.g. atoms, molecules). As a fundamental scientific research field, spectroscopy enables one to determine the existence and structures of new molecular species, (e.g. the 1996 Nobel Prize for Chemistry was awarded for the discovery of C60 - the existence and structure of this molecule was determined by Mass Spectroscopy). This project applies high resolution, Tunable Far Infrared (TuFIR) Spectroscopy to the study of molecular species in the gas phase. Following its development in the 1980’s there are currently seven groups using TuFIR Spectroscopy world-wide; the Cambridge spectrometer is unique in the UK.


Free radicals are chemically reactive molecules which persist for very short times, i.e. they react with other molecules almost as quickly as they are formed. They are of particular importance in atmospheric chemistry and play a major role in the production of the Ozone Hole. In atmospheric cycles, free radicals are established as precursors, intermediates, and products of reactions. The most abundant of these radicals have been identified by low resolution, Far Infrared (FIR) Spectroscopy of the Earth’s stratosphere using satellite, aircraft and balloon borne spectrometers. There are two ways in which TuFIR Spectroscopy is applied in the laboratory to studies of atmospherically important radicals;

  • Pressure/temperature line-broadening studies of single rotational transitions are used to calculate pressure/temperature broadening coefficients. These are then used to compute radical concentrations in the stratosphere.

  • Spectroscopic studies of short-lived radicals are used to determine their existence and structure. Once the radical has been identified from its spectrum its role in atmospheric cycles can be evaluated. A knowledge of the radical structure makes it much easier to predict plausible reaction mechanisms.
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