Eur. Phys. J. D 52, 43-46 (2009)
https://doi.org/10.1140/epjd/e2008-00274-0

Photon-trap spectroscopy of size-selected free cluster ions: “direct” measurement of optical absorption of Ag ⁺ ₉

¹ Cluster Research Laboratory, Toyota Technological Institute, 717-86 Futamata, Ichikawa, Chiba, 272-0001, Japan
² East Tokyo Laboratory, Genesis Research Institute, Inc., 717-86 Futamata, Ichikawa, Chiba, 272-0001, Japan

Corresponding author: ^a terasaki@clusterlab.jp

Received: 19 September 2008
Published online: 24 January 2009

Abstract

An absorption spectrum of size-selected free cluster ions has been measured “directly” via extinction of light without relying on photodepletion/dissociation spectroscopy. The novel technique employs an ion trap and an optical cavity; cluster ions stored in an ion trap interact with photons trapped in a cavity. The storage lifetime of photons in the cavity provides “direct” observation of extinction of light (photon-trap spectroscopy, which is a generalized scheme of cavity ring-down spectroscopy). The first measurement is performed on ultraviolet absorption of Ag₉⁺. Temperature dependence of the spectrum is presented by cooling the ion trap down to 10 K.