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Femtosecond multicolor transient absorption spectroscopy of colloidal silver nanoparticles |
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| Authors: | A. Gaál I. Bugár I. Capek L. Fialová T. Pálszegi V. Sz?cs A. ?atka F. Uherek |
| Affiliation: | (1) Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynská dolina, 842 48 Bratislava, Slovakia;(2) International Laser Centre, Ilkovičova 3, 841 04 Bratislava, Slovakia;(3) Polymer Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 842 36 Bratislava, Slovakia;(4) Institute of Technology, Slovak Academy of Sciences, Dúbravská cesta 9, 845 13 Bratislava, Slovakia;(5) Faculty of Natural Sciences, Comenius University, Mlynská Dolina, 842 15 Bratislava, Slovakia |
| Abstract: | Time-resolved femtosecond multicolor absorption spectroscopy of silver nanoparticle (NP) colloids with particle diameter in range of 10–30 nm is presented. The amplified femtosecond excitation of the surface plasmon resonance band resulted in transient absorption spectra reflecting the electron-phonon relaxation dynamics, which takes place on the early picosecond time scale. The monitored band with enhanced absorption in the 490–540 nm spectral range exhibited red-shift with increasing pump fluency from 0.4 mJ/cm2 to the 1.5 mJ/cm2 level. The growth of the relaxation time with increasing pump fluency reveals the temperature dependent relaxation dynamics caused by the nanometer sized electron confinement in the case of silver. This effect was confirmed also by identification of the relaxation time dependence on the particle diameter at constant pump fluency. The complex experimental results revealed nonlinearities both in the laser excitation and electron relaxation processes. |
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