Ground-state spectroscopy of multiply charged anions in the gas phase

• Applicant: Dr. Sebastian George
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 392290622

Multiply charged anions (MCAs) are common building blocks in condensed phases. Their existence in solids as well as solutions is well established since many decades. Nevertheless, the nature and fundamental properties of isolated MCAs, unaffected by stabilizing counterions and ligands, have been unfathomed due to their fragility in gas-phase experiments. A dedicated experimental program addressing ground state properties of isolated MCAs requires ultra-high vacuum conditions to suppress ion loss of these rarely produced, highly reactive species. Furthermore, lowest blackbody radiation is crucial in order to prevent their destruction by photo-detachment. In my previous work and preliminary studies employing the Cryogenic Trap for Fast ion beams (CTF) and the Cryogenic Storage Ring (CSR) at the Max-Planck-Institut für Kernphysik in Heidelberg I have demonstrated the versatility of electrostatic storage devices at cryogenic temperatures for quasi background-free spectroscopy experiments. For example, the use of laser-induced delayed electron detachment for monitoring precisely the evolution of the internal energy offers new insights into the dynamics of complex molecular systems.With the advent of novel cryogenic storage ring setups experimental studies are mainly limited by an insufficient production of the weakly-bound anionic systems in their rovibrational ground states. Thus, I propose to develop a cryogenic 3-state digital ion trap at the University of Greifswald for creating MCAs in their lowest rovibrational states. This setup will first serve exploring the smallest, extremely weakly bound multiply charged anionic systems. In particular, I will search for the smallest dianionic cluster systems that are stable against electron loss. In a second step, I suggest combining the cryogenic 3-state digital ion trap setup with the CSR in Heidelberg. Here, the ion trap will be used to create, accumulate, and cool bunches of MCAs in their lowest quantum states for injection into CSR. I will study lifetimes, ion-electron interactions, and ion-photon interactions to determine basic aspects such as binding energies and electron-electron correlation effects of MCAs. A key experiment will be the lifetime measurement of the metastable dianionic fullerene C602-. In general these experiments will shed light on the basic properties of MCAs and their role in nature. A successful demonstration of the 3-state ion trap as ion injector will certainly trigger its application in many experiments worldwide.

• DFG Programme: Research Grants