Synchrotron and laser-based gas-phase spectroscopy of radicals and other unusual molecules

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A fundamental key to unlocking the structure and the internal physics of molecules lies in understanding patterns in the colours of light that they absorb and emit. We obtain these patterns - the molecular spectrum - by probing the molecules with lasers, or with other light sources. Since the spectrum is a unique identifier for a particular molecule, we can determine important information about the composition of the atmosphere, or of astrophysical objects like comets, nebulae, stars, and the interstellar medium, by comparing spectra obtained from these objects to those obtained on Earth. In our laboratory at the University of New Brunswick, my students experiment on metal-bearing molecules that we create in a fast-moving molecular jet, and probe them with laser beams directed at right angles to the jet. We also use lasers to probe molecules featuring a backbone composed of a string of carbon atoms, which we create by subjecting carbon-bearing gases to electrical discharges. In both cases, the molecules of interest are highly reactive and unstable radicals, present in only trace amounts and requiring techniques of very high sensitivity to study. Such molecules are frequently found in astrophysical environments where the density of material with which they can react is very low. The construction of the Canadian Light Source synchrotron in Saskatoon, SK has added an exciting new possibility for molecular spectroscopy experiments - access to intense and well-collimated light at very long wavelengths. The synchrotron light allows us to rapidly acquire spectra of extremely high quality in the difficult 2-30 terahertz region of the electromagnetic spectrum, where the fundamental vibrations of many larger molecules of astrophysical interest lie. Many currently-active satellite-borne instruments are sensitive to this region, and the data my students and I collect provides a valuable database for comparison with the spectra these satellites collect from the universe around us.