  In this work we use femtosecond laser pulses of 800 nm wavelength to excite
and characterize the multiphoton luminescence emission of single gold
nanoparticles. For excitation with 100 fs laser pulses we observe a two and
three photon emission dominated by radiative electron hole pair recombination,
while the emission is caused by radiative plasmon decay for excitation with 500
fs pulses. For single gold nanorods with different aspect ratios, we study the
interplay between the particle plasmon and electron hole pairs, which enables
us to develop a quantitative model to fully describe the two and three photon
luminescence emission of single gold nanoparticles.
