Quantum state resolved few-body collisions and reactions at ultralow temperatures

• Applicant: Professor Dr. Johannes Hecker Denschlag
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 399903135

While three- and four-body collisions of atoms are some of the most fundamental processes in nature, they are still not fully understood. In order to answer some of the important, open questions, we propose here to experimentally investigate such few-body collisions in the ultracold regime in a fully state-resolved manner. Using ultracold 87Rb atoms and 87Rb2 molecules we prepare an initial quantum state of colliding particles and after the collision we measure the quantum states of the diatomic products. For this, we will employ and further develop a highly selective detection method that our group has recently discovered. It is based on resonance-enhanced multi-photon ionization of molecules and an efficient subsequent ion detection. We will study two different kinds of collisional processes: 1) Three-body recombination of 87Rb where a Rb2 molecule is formed. 2) Relaxation of an excited ultracold Rb2 molecule to a more deeply bound state in a collision with either a Rb atom or another Rb2 molecule. Our experiments tackle the novel research field of ultracold chemistry which only recently has become accessible. Therefore we expect our research to deliver a large number of new insights. Besides gaining a fundamental understanding of ultracold reactive or inelastic few-body collisions, an important incentive for our work is to learn how to gain control over chemical reactions. We expect that the proposed experiments will lead the young field of cold state-to-state chemistry, in particular for systems with many reaction paths.

• DFG Programme: Research Grants