A conclusive demonstration of vibrational pumping and determination of   SERS cross sections
  We provide conclusive demonstration of vibrational pumping under Surface Enhanced Raman Scattering (SERS) conditions by performing anti-Stokes/Stokes ratio measurements down to 10 K using dried silver colloids, the dye rhodamine 6G and 676 nm laser excitation. The method we propose allows the measurement of the SERS cross sections for different modes and the determination of the asymmetry between the anti-Stokes and Stokes SERS cross sections. 
R. C. Maher, P. G. Etchegoin, E. C. Le Ru, L. F. Cohen