A broadly tunable quantum cascade laser for spectroscopic characterization

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Water plays an active role in stabilizing biological structures and facilitating biological functions. Significant current research efforts are directed toward determining absolute configurations of biomolecules in their (natural) aqueous environment. To achieve this ultimate goal, it is essential to develop an adequate theoretical description of solvation of chiral molecules in aqueous solution.While the solution phase measurements provide information on the combined effects of an enormous amount of intra- and intermolecular hydrogen bonding in solution, it is extremely difficult, if not impossible, to uncover the underlying mechanisms without detailed and accurate experimental input on the molecular level. One of our approaches to tackle this challenge is to apply jet-cooled high resolution infrared laser spectroscopy to characterize the stepwise solvation of a chiral molecule by several water molecules. Studies of these model molecular systems in a well controlled molecular beam environment will allow us to assess the influence of various effects separately. Such a stepwise approach will be extremely valuable for developing a new theoretical description of solvation.A monumental milestone was reached recently in quantum cascade laser (QCL) development with the realization of continuous wave external cavity QCLs that have wide frequency tunability, narrow line width, excellent output power, and super mode quality. These key characters make them an ideal laser source for high resolution infrared laser spectroscopy. We will take advantage of this timely development and implement such a QCL into our recently completed cavity enhanced absorption spectrometer. Funds are requested to purchase an external cavity QCl and a pair of cavity ring down mirrors centred at 6.2µm region. These are two essential components that we need for the spectroscopic characterization of the chiral molecule-(water)_n clusters.