Jeffries William R, Malola Sami, Tofanelli Marcus A, Ackerson Christopher J, Häkkinen Hannu, Knappenberger Kenneth L
Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Department of Physics, Nanoscience Center, University of Jyväskylä, Fl-40014 Jyväskylä, Finland.
J Phys Chem Lett. 2023 Jul 27;14(29):6679-6685. doi: 10.1021/acs.jpclett.3c01477. Epub 2023 Jul 18.
The coherent vibrational dynamics of Au(SCH), obtained from femtosecond time-resolved transient absorption spectroscopy, are described. Two acoustic modes were identified and assigned, including 2.0 THz breathing and 0.7 THz quadrupolar vibrations. These assignments are consistent with predictions using classical mechanics models, indicating that bulk models accurately describe the vibrational properties of Au(SCH). Coherent phonon signals were persistent for up to 3 ps, indicating energy dissipation by the nanocluster was the primary dephasing channel. The initial excitation phases of the breathing and quadrupolar modes were π-phase-shifted, reflecting differences in the displacive nuclear motion of the vibrations. The combined agreement of the vibrational frequencies, relative phases, and decoherence times supported predictions based on classical models. The vibrational frequencies were insensitive to silver substitution for gold but did show increased inhomogeneous damping of the coherent phonons. The ability to predict the vibrational properties of metal nanoclusters can have an impact on nanoresonator and mass sensing technologies.
描述了通过飞秒时间分辨瞬态吸收光谱法获得的Au(SCH)的相干振动动力学。识别并指定了两种声学模式，包括2.0太赫兹的呼吸振动和0.7太赫兹的四极振动。这些指定与使用经典力学模型的预测一致，表明体模型准确地描述了Au(SCH)的振动特性。相干声子信号持续长达3皮秒，表明纳米团簇的能量耗散是主要的退相通道。呼吸振动和四极振动的初始激发相位发生了π相移，反映了振动中位移核运动的差异。振动频率、相对相位和退相干时间的综合一致性支持了基于经典模型的预测。振动频率对用银取代金不敏感，但确实显示出相干声子的非均匀阻尼增加。预测金属纳米团簇振动特性的能力可能会对纳米谐振器和质量传感技术产生影响。
