S. Haze et. al Phys. Rev. Lett. 128, 133401 (2022)

We explore the physical origin and the general validity of a propensity rule for the conservation of the hyperfine spin state in three-body recombination. This rule was recently discovered for the special case of Rb87 with its nearly equal singlet and triplet scattering lengths. Here, we test the propensity rule for Rb85 for which the scattering properties are very different from Rb87. The Rb2 molecular product distribution is mapped out in a state-to-state fashion using resonance-enhanced multiphoton ionization detection schemes which fully cover all possible molecular spin states. Interestingly, for the experimentally investigated range of binding energies from zero to ∼13  GHz×h we observe that the spin-conservation propensity rule also holds for Rb85. From these observations and a theoretical analysis we derive an understanding for the conservation of the hyperfine spin state. We identify several criteria to judge whether the propensity rule will also hold for other elements and collision channels.

 

Life and death of a cold BaRb⁺ molecule inside an ultracold cloud of Rb atoms

A. Mohammadi et. al. Phys. Rev. Research 3, 013196 (2021)

We study the evolution of a cold single ${\mathrm{BaRb}}^{+}$ molecule while it continuously collides with ultracold Rb atoms. The initially weakly bound molecule can undergo a sequence of elastic, inelastic, reactive, and radiative processes. We investigate these processes by developing methods for discriminating between different ion species, electronic states, and kinetic ion energy ranges. By analyzing the experimental data while taking into account theoretical insights, we obtain a consistent description of the typical trajectory through the manifold of available atomic and molecular states. Monte Carlo simulations describe the measured dynamics well. As a further result, we determine rates for collisional and radiative relaxation as well as photodissociation, spin-flip collisions, and chemical reactions.

Obvervation of spin-orbit-dependent electron scattering using long-range Rydberg molecules

M. Deiß et. al. Phys.Rev. Research 2, 013047 (2020)

We present experimental evidence for spin-orbit interaction of an electron as it scatters from a neutral atom. The scattering process takes place within a ${\mathrm{Rb}}_2$ ultralong-range Rydberg molecule, consisting of a Rydberg atomic core, a Rydberg electron, and a ground state atom. The spin-orbit interaction leads to characteristic level splittings of vibrational molecular lines which we directly observe via photoassociation spectroscopy. We benefit from the fact that molecular states dominated by resonant $p$-wave interaction are particularly sensitive to the spin-orbit interaction. Our work paves the way for studying novel spin dynamics in ultralong-range Rydberg molecules. Furthermore, it shows that the molecular setup can serve as a microlaboratory to perform precise scattering experiments in the low-energy regime of a few meV.

The team (left to right)

• Dr. Markus Deiß
• Dominik Dorer
• Dr. Shinsuke Haze
• Prof. Dr. Johannes Hecker Denschlag