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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Excitation wavelength and fluence dependent femtosecond transient absorption studies on electron dynamics of gold nanorods
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Excitation wavelength and fluence dependent femtosecond transient absorption studies on electron dynamics of gold nanorods

机译：激发波长和能量密度依赖的飞秒瞬态吸收研究金纳米棒的电子动力学

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摘要

The electron dynamics of gold nanorods were systematically studied by using femtosecond transient absorption experiments. Two different excitation wavelengths (400 and 800 nm) have been used as the excitation sources to selectively excite transverse and longitudinal modes. The transient absorption spectra were found to be strongly dependent on the excitation wavelength and fluence. Laser pulses of 800 nm excite the longitudinal mode directly, which cause an increase in the electronic temperatures and subsequent broadening and bleaching of both the longitudinal and transverse modes. Pulses of 400 nm excite both the transverse and longitudinal modes simultaneously. At low excitation fluences, the energy is distributed into two modes according to their steady state extinction coefficients, under which the transient spectra are similar to those under excitation at 800 nm. However, as the excitation fluence exceeds a threshold, the bleaching of the longitudinal plasmon band saturates and the input energies mainly flow to the transverse mode. As a result, the bleaching of the transverse mode increases rapidly. The electron - phonon dynamics show a strong correlation with the bleaching amplitude. We have tried to explain the results with a consistent picture: the bleaching amplitude and electron - phonon relaxation time are directly related to energy distribution into different modes, which are excitation wavelength and fluence dependent. Our studies help to clarify the seemingly inconsistent results in the previous studies by different research groups.
机译：利用飞秒瞬态吸收实验系统地研究了金纳米棒的电子动力学。两种不同的激发波长（400和800 nm）已用作激发源，以选择性激发横向和纵向模式。发现瞬态吸收光谱强烈依赖于激发波长和能量密度。 800 nm的激光脉冲直接激发纵向模式，这会导致电子温度升高，并随后使纵向模式和横向模式变宽和漂白。 400 nm的脉冲同时激发横向和纵向模式。在低激发通量下，能量根据其稳态消光系数分为两种模式，在该模式下，瞬态光谱与在800 nm激发下的瞬态光谱相似。然而，当激发通量超过阈值时，纵向等离子体激元带的漂白饱和，并且输入能量主要流向横向模式。结果，横向模式的漂白迅速增加。电子-声子动力学与漂白幅度显示出很强的相关性。我们试图用一致的图片来解释结果：漂白幅度和电子-声子弛豫时间与能量分配成不同模式直接相关，这些模式取决于激发波长和注量。我们的研究有助于弄清不同研究小组在以前的研究中似乎不一致的结果。

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