wave at the ultra award winning technique

John Broughall

Laboratory Update, May, pp. 12-13 (2002)

Numerous techniques are routinely used for the analysis and characterisation of materials.  The majority employ traditional spectroscopy i.e. the measurements of the characteristics of electromagnetic waves propagating through the analysed sample. This includes optical spectroscopy, fluorescents, infra-red, NMR and others. Now, a new spectroscopy can be added to the list which has been developed to exploit the analytical power of ultrasonic waves. This technique adds superior analytical capabilities and provides a method for accurate and non-destructive sample fingerprinting. Ultrasonic spectroscopy relies on the principle that ultrasonic (high frequency acoustic) waves travel at different speeds in different media fastest through solids, more slowly through liquids and slowest of all through gases and attenuates differently. If the velocity and attenuation of these waves can be measured as they travel through a sample, then diagnostic information can be gleaned about the composition,  structure and molecular processes in the sample. Ultrasonic waves are, potentially, an excellent method for characterising samples, as they can pass through most materials, including those which are optically opaque. And, in contrast to other analytical techniques which look at the electric or magnetic properties of a material, they probe its elastic properties. These are extremely sensitive to intermolecular interactions.

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