This project examined the time evolution of spectral blinking behavior of single molecule surface-enhanced Raman spectra (SERS).
For the molecules examined, it was found that the on−off behavior of the spectral lines was not always in tandem and that the spectral lines can be divided into subsets with separate tandem blinking behavior. One group, despite fluctuating somewhat, was relatively steady in intensity, until they either abruptly or sometimes more gradually disappeared. A second group blinked more sharply, on briefly or off for a longer period. They appeared more erratically and often were more intense while on. The former set of lines was found to obtain most of their intensity through Franck−Condon terms in the polarizability expression, while lines for which the Raman intensity is correlated with vibronic coupling tended to blink with sharper on−off differences. These observations are interpreted in terms of the theory of vibronic coupling as applied to SERS. (publisher abstract modified)