STM Combined With Fluorescence Spectroscopy

Kuhn et al. observed the fluorescence enhancement and fluorescence decay rate of a single terrylene molecule when a spherical gold nanoparticle was approached to the 

Nishitani et al. observed the tip-enhanced fluorescence of 8 nm thick meso-tetralds (3,5-di-tertiarybutyl-phenyl)porphyrin (H2TBPP) films on ITO with an Ag tip [38]. They reported that the fluorescence was enhanced by the locally confined electromagnetic field in the vicinity of the tip. The enhancement factor is evaluated to be larger than 2000. 

First we consider the electronic excitation probability Pekc for a single molecule during a single laser pulse. When a molecule has the absorption coefficient Eabs(dm mol cm ), its absorption cross section Gabs is given by 3.81 x lO Sabs cm molecule . Since the probability Peiec is proportional to the light intensity (photons s cm ) under the objective lens, it is given by 

The next step is to estimate how long a molecule can stay in its vibrational excited state during a single electric pulse. A conventional electronic circuit carmot generate a short pulse like 10 ps, so that the use of electric pulses longer than 100 ps is more 

In summary, recent progress and future prospects in the research field of fiuorescence and Raman spectroscopy combined with STM in order to achieve high spatial resolution spectroscopy have been reviewed. In the near future, single (sub-) molecule STM spectroscopy is expected to be applied to the nano-world of science and engineering. 

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