Cold atom-atom-ion three-body recombination of 4He-4He-X- (X = H or D)

Mediated Interaction between Ions in Quantum Degenerate Gases

We explore the interaction between two trapped ions mediated by a surrounding quantum degenerate Bose or Fermi gas. Using perturbation theory valid for weak atom-ion interaction, we show analytically that the interaction mediated by a Bose gas has a power-law behavior for large distances whereas it has a Yukawa form for intermediate distances. For a Fermi gas, the mediated interaction is given by a power law for large density and by a Ruderman-Kittel-Kasuya-Yosida form for low density. For strong atom-ion interaction, we use a diagrammatic theory to demonstrate that the mediated interaction can be a significant addition to the bare Coulomb interaction between the ions, when an atom-ion bound state is close to threshold. Finally, we show that the induced interaction leads to substantial and observable shifts in the ion phonon frequencies.

Scattering length scaling rules for atom-atom-anion three-body recombination of zero-energy 4He4He6Li- system

The scattering length scaling rules for three-body recombination (TBR) of the 4He4He6Li- system in the zero-energy limit (E → 0) are investigated by considering various post-Born-Oppenheimer (post-BO) contributions to the standard BO potential of He-He interaction. It is found that these post-BO effects on the TBR rates that lead to different dimer products could be well fitted by the scattering length scalings Cab with a being the scattering length of the He-He interaction, and b and C the constants. It is interesting to find that the powers b about both the weakly and deeply bound dimer products are quite different from the well-known powers given by the scattering length scaling laws in the fields of ultracold neutral atomic gases. Such difference and the distinct powers associated with various dimer products are qualitatively accounted for by the properties of the major effective potentials and relatively long-range nonadiabatic couplings. Particularly, from these properties, the scaling powers are expected to be dependent on systems, but the power scattering length scaling behaviors to be universal, which has also been checked to apply to a wide range of a by tuning the He-He interaction.

Cold atom-atom-anion three-body recombination of 4He4HexLi- (x = 6 or 7) systems

Atom-atom-anion three-body recombination (TBR) in mixed ⁴He and ^xLi^- (x = 6 or 7) is investigated in the adiabatic hyperspherical representation by quantum mechanically solving the Schrödinger equation. The distributions of product states following these TBR processes are found to be relatively different for the two systems when the collision energy is less than roughly 0.6 mK × k_B or 0.3 mK × k_B for ⁴He⁴He⁶Li^- and ⁴He⁴He⁷Li^- systems, respectively, with k_B being the Boltzmann constant. For ⁴He⁴He⁶Li^- systems, the rate of recombination into (v=0) l = 0⁴He⁶Li^- molecular anions is the largest with v and l denoting the rovibrational quantum numbers, while the TBR rate that leads to the formation of l = 1⁴He⁶Li^- molecular anions is a little smaller than that of neutral ⁴He₂ molecules. For ⁴He⁴He⁷Li^- systems, neutral ⁴He₂ molecules tend to be the most products, following the yields of l = 0 and 1 ⁴He⁷Li^- molecular anions. However, in spite of these distinctly different distributions, the products of molecular anions, the sum of l = 0 and 1 ⁴He^xLi^- products, are relatively larger than that of neutral ⁴He₂ molecules for both the two systems.