  We use ultrafast pump-probe transmission spectroscopy to measure the
electronic relaxation time for electrons in cobalt nanoparticles embedded on
glass substrate using femtosecond laser pulses. We found that the plasmon
excitation is inhomogenously broadening with a fast excitation time of 23 fs.
and a plasmonic relaxation time of 97fs. The femtosecond laser pulses used in
this experiment were come from a Ti:Sapphire resonator that uses a
self-mode-locking mechanism based on the nonlinear Kerr effect. The pulses were
found to have repetition rate of 103.52MHz with a pulse width of 64.5 fs at
FWHM, and 810nm center wavelength.
