%0 Journal Article %J Physical Review B %D 2005 %T Femtosecond excitation dynamics in gold nanospheres and nanorods %A Varnavski, O. P. %A Goodson, T. %A Mohamed, MB %A El-Sayed, Mostafa A %X Femtosecond visible photoluminescence is detected from gold nanoparticles using time-resolved fluorescence upconversion spectroscopy. We directly compared this fast luminescence from gold nanospheres (subset of 25 nm) with that obtained from nanorods (subset of 15x40 nm, subset of 15x27 nm) under vis (3.02 eV) and UV(4.65 eV) excitation. A fast (similar to 50 fs) decay was obtained for the nanoparticles and the emission was depolarized. Degenerate femtosecond pump-probe experiments in the low excitation intensity regime demonstrated much slower electron thermalization and/or equilibration dynamics on the time scale of a few hundred femtoseconds. These features strongly indicate a d-hole-conduction electron recombination process as the origin of this photoluminescence. A direct comparison of the fast emission spectra from nanorods and nanospheres is used to discuss the emission enhancement mechanism. These results suggest that the classical local field enhancement theory describes quantitatively well many of the emission features of nanorods with respect to those for nanospheres without invoking more complex models. %B Physical Review B %V 72 %8 Dec %@ 1098-0121 %G eng %M WOS:000234336000094 %] 235405 %R 10.1103/PhysRevB.72.235405 %0 Journal Article %J The Journal of Physical Chemistry B %D 2003 %T Relative enhancement of ultrafast emission in gold nanorods %A Varnavski, O. P. %A Mohamed, MB %A El-Sayed, Mostafa A %A Goodson III, T. %X Time-resolved fluorescence spectroscopy has been employed to probe the ultrafast emission observed in gold nanospheres and nanorods. The decay of the emission was found to be ≤50 fs. The ultrafast emission from nanorods has been directly compared to that for nanospheres and the dispersion of the relative local field enhancement factor was obtained and compared with calculations. Measurements with both visible and ultraviolet excitations have been analyzed. These results give the first observation and analysis of the mechanism for the local field-enhanced ultrafast emission in gold nanorods and nanospheres. %B The Journal of Physical Chemistry B %I ACS Publications %V 107 %P 3101-3104 %@ 1520-6106 %G eng %U http://dx.doi.org/10.1021/jp0341265 %N 14 %R 10.1021/jp0341265