Universality and chaoticity in ultracold K+KRb chemical reactions

Abstract

A fundamental question in the study of chemical reactions is how reactions proceed at a collision energy close to absolute zero. This question is no longer hypothetical: quantum degenerate gases of atoms and molecules can now be created at temperatures lower than a few tens of nanokelvin. Here we consider the benchmark ultracold reaction between, the most-celebrated ultracold molecule, KRb and K. We map out an accurate ab initio ground-state potential energy surface of the K2Rb complex in full dimensionality and report numerically-exact quantum-mechanical reaction dynamics. The distribution of rotationally resolved rates is shown to be Poissonian. An analysis of the hyperspherical adiabatic potential curves explains this statistical character revealing a chaotic distribution for the short-range collision complex that plays a key role in governing the reaction outcome.

Magnetically tunable Feshbach resonances in ultracold gases of europium atoms and mixtures of europium and alkali-metal atoms

“…For ultracold collisions of Dy and Er atoms it was measured [16,25] and theoretically confirmed [16,44,[64][65][66][67] that the interplay of anisotropic electronic and dipolar interactions leads to the chaotic spectra of Feshbach resonances being the signature of the level repulsion following the predictions of the Gaussian Orthogonal Ensemble of random matrices [68]. Similar results were predicted for atom-molecule collisions [69][70][71]. To verify the above hypothesis in the considered case, in Fig.…”

Universal Scattering of Ultracold Atoms and Molecules in Optical Potentials

“…Exact quantum-mechanical results for KRb + K and LiYb + Li with molecules in the X 1 Σ + and X 2 Σ + potentials, respectively, have been published in References [23,24], respectively. They are compared to the s-wave contribution to the rate coefficient predicted by the universal model as well as its summed, total value in Figure 4.…”

“…For rotation-less molecules, the van-der-Waals dispersion potential is isotropic. In a number of cases [23][24][25] these QDT results have been validated with comparisons with "exact" quantum simulations.…”

“…Such detailed understanding of the ultracold reaction might require a rigorous quantum treatment. Initial examples are the theoretical simulations of the state-to-state reaction rate for LiYb + Li and KRb + K using a numerically-exact quantum-mechanical (EQM) method formulated in hyperspherical coordinates [23,24]. These simulations led to a better understanding of the reaction mechanism and product ro-vibrational distribution and might also guide the development of experimental state-selective detection tools.…”

Quantum Scattering in an Optical Collider for Ultracold Atoms

“…We will also investigate further shape resonances, such as an = 6 shape resonance in 87 Rb and an = 4 shape resonance in 40 K-87 Rb collisions. We can also associate molecules near a Feshbach resonance and measure atom-dimer scattering properties [26].…”