Photo-ionization is a fundamental process in nature and has been used as a tool to study the inner structure of matter from the early days of quantum mechanics. Single photon ionization is conventionally understood as emission of an electron in state-to-state processes. Other photon-induced ionization processes, of which thermionic emission is the best known, involve absorption of several photons and proceed as a thermal process. Recently, it was shown that C₆₀ can ionize in a quasi-thermal process after the absorption of a single photon [1]. The mechanism suggested for the phenomenon invokes the creation of an intermediate state of hot electrons, with temperatures on the order of 10⁴ K and lifetimes of a few hundred femtoseconds. The talk will present the experimental background and the first simpleminded explanation of this new phenomenon.

References: [1] Klavs Hansen, Robert Richter, Michael Alagia, Stefano Stranges, Luca Schio, Peter Salen, Vasyl Yatsyna, Raimund Feifel, and Vitali Zhaunerchyk, Single Photon Thermal Ionization of C₆₀ , Phys. Rev. Lett. 118 103001 (2017)

Prof. Klavs Hansen has joined Tianjin International Center of Nanoparticles and Nanosystems of Tianjin University since summer 2016. He did his PhD work at the Niels Bohr Institute on the electronic shell structure of metal clusters. Prof. Klavs Hansen's research interests are: 1) Quantal and statistical processes in nanoscale quantum systems; 2) Thermodynamics of free clusters and the approach to thermal equilibrium. He has published 137 peer reviewed papers (H-index=32). He is the author of the book "Statistical Physics of Nanoparticles in the Gas Phase"(Springer 2013).