[Au25(SR)18]-团簇的相干振动动力学研究

利用飞秒时间分辨光谱，可观测叠加在电子态动力学上的相干振动动力学. 从金团簇的相干振动中，不仅能提取电子与振动的耦合信息，也能得到力学性质和电子结构，进而有望实现微小质量探测等应用. 本文利用飞秒时间分辨的瞬态吸收探测了Au₂₅(SR)₁₈]^-团簇的相干振动动力学，通过对相干振动的频率、相位、波长分布的详细分析进一步揭示了其来源. 在Au₂₅(SR)₁₈]^-团簇的飞秒瞬态吸收动力学中可以观测到频率为40 cm^-1和80 cm^-1的两种振动，均来源于团簇中心Au₁₃核的振动. 通过对相干振动的相位分析发现频率为80 cm^-1的振动来自于对电子态之间吸收频率的调制，而频率为40 cm^-1的振动来源于对电子态之间吸收强度的调制. 同时，研究发现Au₂₅(SR)₁₈]^-团簇相干振动的频率对其表面配体不敏感，该振动是来源于Au₁₃核的本征性质.

Coherent Vibrational Dynamics of [Au25(SR)18]- Nanoclusters

Coherent vibrational dynamics can be observed in atomically precise gold nanoclusters using femtosecond time-resolved pump-probe spectroscopy. It can not only reveal the coupling between electrons and vibrations, but also reflect the mechanical and electronic properties of metal nanoclusters, which holds potential applications in biological sensing and mass detection. Here, we investigated the coherent vibrational dynamics of Au₂₅(SR)₁₈]^- nanoclusters by ultrafast spectroscopy and revealed the origins of these coherent vibrations by analyzing their frequency, phase and probe wavelength distributions. Strong coherent oscillations with frequency of 40 cm^-1 and 80 cm^-1 can be reproduced in the excited state dynamics of Au₂₅(SR)₁₈]^-, which should originate from acoustic vibrations of the Au₁₃ metal core. Phase analysis on the oscillations indicates that the 80 cm^-1 mode should arise from the frequency modulation of the electronic states while the 40 cm^-1 mode should originate from the amplitude modulation of the dynamic spectrum. Moreover, it is found that the vibration frequencies of Au₂₅(SR)₁₈]^- obtained in pump-probe measurements are independent of the surface ligands so that they are intrinsic properties of the metal core. These results are of great value to understand the electron-vibration coupling of metal nanoclusters.