  We measure nonlinear optical scattering from individual Au nanorods excited
by ultrafast laser pulses on resonance with their longitudinal plasmon mode.
Isolating single rods removes inhomogeneous broadening and allows the
measurement of a large nonlinearity, much greater than that of nanorod
ensembles. Surprisingly, the ultrafast nonlinearity can be attributed entirely
to heating of conduction electrons and does not exhibit any response associated
with coherent plasmon oscillation. This indicates a previously unobserved
damping of strongly driven plasmons.
