CRIF:ID- Development of an Ultrabroad Bandwidth UV-Visible Cavity Enhanced Spectroscopy Spectrometer

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This is an award from the CRIF:ID program to Kevin K. Lehman in the Chemistry Department at the University of Virginia, Azer Yalin, Mechanical Engineering Department, Colorado State University and Sonia M. Kreidenweis, Atmospheric Science Department, Colorado State University. In the development project optical cavities based upon CaF2 prisms will be designed, fabricated, tested and characterized. Because of the substantially lower Rayleigh scattering of this material, it is anticipated that these prisms will be useful throughout the near and much of the mid-UV spectral regions as well as the visible. This spectral region covers the lowest electronic transitions of most molecules. The use of these prisms will allow a dramatic improvement in sensitivity over conventional absorption techniques and absolute concentration determination down to trace levels for species of known absorption cross section. Further, the prism cavity ring-down spectroscopy systems will be integrated with experiments targeted at Molecular Spectroscopy (Lehmann), measurements of sputtering (Yalin), and atmospheric aerosols (Kreidenweis). Spectroscopy is one of the most widely used tools in physical science. Absorption spectroscopy in the UV, visible, and IR spectral regions give information on the molecular and electronic structures of molecules and their interactions with other molecules. In cases where fluorescence is weak, absorption is the most straightforward and practical way to detect optical transitions. While absorption spectroscopy is widely used, it has long suffered from inadequate sensitivity for many applications. In the past two decades, this sensitivity has been dramatically improved, opening up many new applications, by the introduction of Cavity Ring-down Spectroscopy and related methods that exploit low loss (high finesse) optical cavities. The present work will lead to a substantial increase in the spectral range and sensitivity of these methods, particularly in the UV spectral region. The projects will be carried out by graduate students who will learn valuable research and instrument development skills.