Femtosecond correlated optical reactivity and scanning tunneling microscopy studies of metal surfaces

A new experimental technique, correlated optical reactivity and scanning tunneling microscopy (CORSTM), is shown to be a uniquely powerful tool for the study of spatially localized reactivity of surfaces. In particular, CORSTM measurements directly correlate electromagnetic field enhancements that affect chemical dynamics and reactivity with surface topography on the length scale of a few nanometers. These measurements are based on the detection of surface plasmon polariton mediated multi-photon ionization (SPP-MPI) from metal surfaces using ultrafast optical excitation and scanning probe microscopy photoelectron detection. The CORSTM approach is extended to a pump-probe scheme facilitating spatially localized measurement of hot electron dynamics. The experimental results provide direct confirmation of the optimal structural topographies for surface enhanced spectroscopy predicted by electromagnetic theories. CORSTM will provide a better understanding of phenomena that involve plasmons through the direct measurement of structure-function correlations.