New technique measures the strength of individual molecular bonds

Nature : Raman spectroscopy and scanning tunneling microscopes (STMs) have been used together to produce increasingly more detailed images of molecules. A new advancement in the pairing has produced pictures of individual molecules as well as measurements of the strength of the molecules’ bonds. By itself, Raman spectroscopy uses a laser to cause molecules to vibrate, and the way the light is scattered can be used to determine the molecule’s structure. The technique doesn’t work well with small samples. An STM uses a very fine metal tip held just 1 nm from a surface to allow electrons to quantum tunnel across the gap, and the strength of the electric current is used to map surfaces with atomic resolution. An international team of researchers has succeeded in using an STM to narrow the focus of the Raman laser. They use another laser to create oscillations in the STM tip’s electric field. When the frequency of those oscillations matches the frequency of the Raman laser, the beam becomes significantly stronger. At 0.3 nm, the resolution of the new arrangement is still less detailed than that of other techniques, such as atomic force microscopy, but the RamanâSTM pairing allows for measuring the strength of molecular bonds as well.