Single molecule absorption spectroscopy is an extremely sensitive technique for analytical chemistry, for measuring electrical properties of molecules, and for studying energy transfer on surfaces. While most molecules don't fluoresce -- limiting the usefulness of single molecule fluorescence spectroscopy -- all molecules absorb, making single molecule absorption spectroscopy a much more general approach. |
Single molecules don't absorb much light, making detection difficult to begin with. An even bigger problem, however, is that light-induced heating in the sample and in the microscope tip can produce so much noise that the signal is lost. |
This new measurement method combines the chemical selectivity of optical absorption spectroscopy with the atomic-scale resolution of scanning tunneling microscopy. The method literally feels how a molecule changes shape when it absorbs energy. |