High resolution microwave spectroscopy

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This research uses the speeds of rotation of gaseous molecules to determine their geometries.  The method used is analogous to ringing a bell, in which a clapper hits the bell, which then rings at tones (frequencies) characteristic of its shape, size and composition.  In our research the clapper is replaced by a pulse of microwaves which gives the molecules extra energy.  As the molecules lose this energy they emit microwave radiation at characteristic frequencies dictated also by their shape, size and composition.  We use the patterns of the frequencies (the spectrum) to determine the molecular geometries.  Furthermore, we can measure the frequencies so precisely that we can (and do) use small variations from the basic patterns to determine how flexible the molecules are, as well as to obtain information on how the electrons in the molecules (the glue holding the molecule together) are arranged. We are studying small molecules containing metals.  They are prepared by vaporizing solid metal with a laser, and allowing the vapour to react with another substance contained in a noble gas (e.g. argon).  The resulting mixture is then injected as a jet into an evacuated cell.  This procedure holds the molecules long enough for them to be studied. Some specific compounds we are studying are those in which noble gases attach themselves to metals so strongly that the bonding can be considered chemical bonding!  In other work we assess how meaningful physically some of our very precise parameters, particularly bond lengths, really are.