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Trace gas detection: High resolution vibrational spectroscopy of atmospheric molecules

Dr Julia H. Lehman (SoC), Prof. Dwayne Heard (SoC)

Contact email: J.Lehman@leeds.ac.uk

Summary

Alkyl peroxy radicals (RO2) are important intermediates in a variety of atmospheric processes, such as the oxidation of NO to form NO2 (whose subsequent photolysis leads to the formation of tropospheric ozone). However, simple alkyl peroxy radicals, such as methyl peroxy, have yet to be observed in field studies. While the FAGE technique developed here at the University of Leeds offers excellent sensitivity (Onel et al., Atmos. Meas. Tech., 2017, 10, 3985), it relies on an indirect multistep process to characterize the abundance of alkyl peroxy radicals, determined through chemical reaction and subsequent laser-induced fluorescence, and can lack RO2 specificity.

In this project, you will work with a direct detection technique and benchmark the new apparatus against the FAGE technique. You will measure high resolution vibrational absorption spectra at room temperature using a cutting-edge laser-based detection method: cavity-enhanced mid-infrared frequency comb vibrational absorption spectroscopy. As demonstrated by the Ye group at JILA, University of Colorado, Boulder, USA (Bjork et al., Science, 2016, 354, 444), cavity-enhanced frequency comb spectroscopy can be used to simultaneously obtain a broadband and high-resolution vibrational absorption spectrum. You will apply this technique to measure the vibrational absorption spectra of several alkyl peroxy radicals, working towards increasing sensitivity and selectivity. You will interpret the laboratory measurements with the aid of theoretical methods, including quantum chemical calculations and spectroscopic modelling.

This PhD will provide a broad spectrum in training, particularly covering vibrational absorption spectroscopy, kinetic methods, high-resolution laser-based spectroscopic techniques, optics, vacuum systems, and quantum chemical calculations. You will also receive training in writing and implementing computer controlled data acquisition and analysis programs. You will be part of the well-funded, active, and highly collaborative Atmospheric and Planetary Chemistry group within the School of Chemistry.

Please contact Dr Lehman (J.Lehman@leeds.ac.uk) for further details about this opportunity. 

Research website: https://physicalsciences.leeds.ac.uk/staff/216/dr-julia-h-lehman

Click here for a full project description.

Related undergraduate subjects:

  • Atmospheric science
  • Chemistry
  • Electrical engineering
  • Engineering
  • Environmental science
  • Natural sciences
  • Physical science
  • Physics