Abstract
We observed significant transfer of ground state population to the first excited vibrational state by spontaneous surface-enhanced Raman scattering (SERS) which can be explained by unexpectedly large SERS cross sections. Evidence for this pumping includes (i) anti-Stokes to Stokes ratios which exceed those expected from a Boltzmann distribution, (ii) a quadratic dependence of the anti-Stokes signal on the excitation intensity, whereas the Stokes signal remains linearly dependent, and (iii) a component of to Raman transitions in the SERS Stokes signals.
- Received 4 August 1995
DOI:https://doi.org/10.1103/PhysRevLett.76.2444
©1996 American Physical Society