Emergence of surface-plasmon resonance upon metal-cluster growth

2014 Fiscal Year Final Research Report

• Project/Area Number: 25620017
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Physical chemistry
• Research Institution: Kyushu University
• Principal Investigator: TERASAKI Akira 九州大学, 理学(系)研究科(研究院), 教授 (60222147)
• Co-Investigator(Renkei-kenkyūsha): ARAKAWA Masashi 九州大学, 大学院理学研究院, 助教 (10610264)
• Research Collaborator: ITO Tomonori ; TOBITA Kenichiro
• Project Period (FY): 2013-04-01 – 2015-03-31
• Keywords: 金属クラスター / 銀 / 吸収スペクトル / 光解離 / 電子遷移 / 光学応答

Outline of Final Research Achievements

Metal particles exhibit size-dependent features in their optical absorption spectra; an atom shows rich structures in the spectrum originating from single-electron transitions between atomic orbitals, whereas a nanoparticle is characterized by a broad spectrum due to collective excitation of electrons by surface-plasmon resonance. This project focused on elucidation of the change in the character of transitions from single-electron to collective excitation as the particle grows from an atom to clusters, and further to nanoparticles. Photodissociation-action spectroscopy was performed to measure optical absorption spectra of size-selected silver cluster ions (Agn+) in the size range from n = 2 to 35. The spectra below n = 25 showed sharp peaks indicating a single-electron behavior, whereas those of larger sizes were broadened to a structure-less profile, which implies breakup of single-electron excitation at n > 25 toward surface-plasmon resonance of silver nanoparticles.

Free Research Field

ナノ物質科学