Sympathetic Cooling of Large Molecules in a Cold-Atom Trap

• Applicant: Professor Dr. Hanspeter Helm
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: Funded in 2008
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 97830361

Quantum chemistry and computational chemistry can nowadays determine to a high degree of precision internal energy states of even large molecules. Likewise molecular dynamics methods permit time- and space-resolved views of changes in molecular structure, which may occur following interaction with external force fields. Experimental access to microscopic views of such change is generally limited to ensemble averages in an uncontrolled environment to which the molecule is strongly coupled. The long term goal of our project aims at resolving the stochastic development of internal energy states of a single large molecule (size of 102-103 Dalton) in a controlled environment. We anticipate that the quantum nature of the aggregate can be examined, provided it is kept sufficiently long in an environment at sufficiently low temperature. Under such conditions when hot collisions are absent, weak long-range forces as well as the interaction with the thermal black-body background will control the temporal development of an isolated aggregate. In order to achieve such a goal we will attempt to identify and characterize the structural, dynamic, and coherence properties of an isolated and cold macromolecule, embedded in a trapped cloud of laser-cooled atoms, the trap confining the translational motion of both, refrigerant atoms and the macromolecule. We aim to characterize the spectral quantum signatures, which emerge once the macromolecule reaches sub-Kelvin temperatures. From this study, we hope to identify the stochastic cycles of coupling between molecular degrees of freedom and those of the cold rubidium bath, coupling between translation and the internal degrees of freedom of the molecule, energy-transfer from ground-and excitedstate coolant atoms to the macromolecule at sub-thermal energies, as well as the balance of cooling, heating, and clustering in the combined trap and the role of black-body radiation.This ambitious project entails several subprojects, some of which have by this time been completed (see below 2.3) and some which require ongoing research and support by the proposed project (see below 3.3).

• DFG Programme: Research Grants