title: Detection of Recurrent Fluorescence Photons.
abstract: We have detected visible photons emitted from the thermally populated electronic excited state, namely recurrent fluorescence (RF), of C_{6}^{-} stored in an electrostatic ion storage ring. Clear evidence is provided to distinguish RF from normal fluorescence, based on the temporal profile of detected photons synchronized with the revolution of C_{6}^{-} in the ring, for which the time scale is far longer than the lifetime of the intact photoexcited state. The relaxation (cooling) process via RF is likely to be commonplace for isolated molecular systems and crucial to the stabilization of molecules in interstellar environments.
authors.affiliation: Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Ebara
authors.affiliation: Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Furukawa
authors.affiliation: Department of Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Matsumoto
authors.affiliation: Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Tanuma
authors.affiliation: Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.|Atomic, Molecular and Optical Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Azuma
authors.affiliation: Department of Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Haruo
authors.initials: H
authors.lastname: Shiromaru
authors.affiliation: Department of Physics, University of Gothenburg 41296 Gothenburg, Sweden.
authors.forename: Klavs
authors.initials: K
authors.lastname: Hansen