Rydberg molecules: the making and breaking of bonds

C. Wesdorp

Thomas Niederprüm, Oliver Thomas, Tanita Eichert +4 more

Engineering molecules with a tunable bond length and defined quantum states lies at the heart of quantum chemistry. The unconventional binding mechanism of Rydberg molecules makes them a promising candidate to implement such tunable molecules. A very peculiar type of Rydberg molecules are the so-called butterfly molecules, which are bound by a shape resonance in the electron-perturber scattering. Here we report the observation of these exotic molecules and employ their exceptional properties to engineer their bond length, vibrational state, angular momentum and orientation in a small electric field. Combining the variable bond length with their giant dipole moment of several hundred Debye, we observe counter-intuitive molecules which locate the average electron position beyond the internuclear distance.

Donald W. Booth, Seth T. Rittenhouse, J. Yang +2 more

Permanent electric dipole moments are important for understanding symmetry breaking in molecular physics, control of chemical reactions, and realization of strongly correlated many-body quantum systems. However, large molecular permanent electric dipole moments are challenging to realize experimentally. We report the observation of ultralong-range Rydberg molecules with bond lengths of ~100 nanometers and kilo-Debye permanent electric dipole moments that form when an ultracold ground-state cesium (Cs) atom becomes bound within the electronic cloud of an extended Cs electronic orbit. The electronic character of this hybrid class of "trilobite" molecules is dominated by degenerate Rydberg manifolds, making them difficult to produce by conventional photoassociation. We used detailed coupled-channel calculations to reproduce their properties quantitatively. Our findings may lead to progress in ultracold chemistry and strongly correlated many-body physics.

Ch. Jungen

Mingxia Huo

We propose an approach to detect individual Rydberg molecules, where each molecule consists of two atoms lying in different Rydberg states. The scheme exploits the different movements of atoms and molecules in the presence of external forces to differentiate atoms and molecules. The forces acting on the two atoms in the molecule are different. We consider the most ideal situation, that is, the external force is exerted only on one of the two Rydberg atoms in the molecule. The movement of Rydberg atoms that are not affected by the external force depends on whether they are bound to the Rydberg atoms affected by the force. Therefore, bound Rydberg atoms can be distinguished from free Rydberg atoms. By non-destructively resolving the locations of Rydberg atoms through detecting the absorption events with the probe field or the fluorescence signal, the scheme can be utilized to detect the positions of Rydberg molecules, and also the bond force in the Rydberg molecule.

Robert S. Freund