Supersonic cooling dimers

The intensely developing technique of high-resolution IR-spectroscopy of dimers composed of two different molecules in supersonic cooled jets offers a new promising approach to the quantum dynamics of reaction complexes. In essence, this is a unique possibility of modelling low-temperature chemical reactions. 

The shape of the potential surface can be used to determine energy levels and partition functions and consequently the equilibrium constant for van der Waals molecule formation. This is done elsewhere.A typical result is that gaseous argon cooled to near its normal boiling point, where kT = De, contains a few percent of the dimer Ar2- Samples of similarly cooled nitrogen, oxygen, or hydrogen contain comparable concentrations of (N2)2j ( 2)29 r (H2)2-The use of supersonic nozzles produces beams characterized by temperatures often less than 10 K. Under these conditions the beam composition will be dominated by van der Waals molecules. 

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