Within a dense environment (ρ ≈ 10 14 atoms=cm 3 ) at ultracold temperatures (T < 1 μK), a single atom excited to a Rydberg state acts as a reaction center for surrounding neutral atoms.At these temperatures, almost all neutral atoms within the Rydberg orbit are bound to the Rydberg core and interact with the Rydberg atom.We have studied the reaction rate and products for nS 87 Rb Rydberg states, and we mainly observe a state change of the Rydberg electron to a high orbital angular momentum l, with the released energy being converted into kinetic energy of the Rydberg atom.Unexpectedly, the measurements show a threshold behavior at n ≈ 100 for the inelastic collision time leading to increased lifetimes of the Rydberg state independent of the densities investigated.Even at very high densities (ρ ≈ 4.8 × 10 14 cm -3 ), the lifetime of a Rydberg atom exceeds 10 μs at n > 140 compared to 1 μs at n ¼ 90.In addition, a second observed reaction mechanism, namely, Rb þ 2 molecule formation, was studied.Both reaction products are equally probable for n ¼ 40, but the fraction of Rb þ 2 created drops to below 10% for n ≥ 90.Within a dense environment (ρ ≈ 10 14 atoms=cm 3 ) at ultracold temperatures (T < 1 μK), a single atom excited to a Rydberg state acts as a reaction center for surrounding neutral atoms.At these temperatures, almost all neutral atoms within the Rydberg orbit are bound to the Rydberg core and interact with the Rydberg atom.We have studied the reaction rate and products for nS 87 Rb Rydberg states, and we mainly observe a state change of the Rydberg electron to a high orbital angular momentum l, with the released energy being converted into kinetic energy of the Rydberg atom.Unexpectedly, the measurements show a threshold behavior at n ≈ 100 for the inelastic collision time leading to increased lifetimes of the Rydberg state independent of the densities investigated.Even at very high densities (ρ ≈ 4.8 × 10 14 cm -3 ), the lifetime of a Rydberg atom exceeds 10 μs at n > 140 compared to 1 μs at n ¼ 90.In addition, a second observed reaction mechanism, namely, Rb þ 2 molecule formation, was studied.Both reaction products are equally probable for n ¼ 40, but the fraction of Rb þ 2 created drops to below 10% for n ≥ 90.

arXiv:1605.04883Physical Review XAug 10, 201686 citations

Ultracold Rydberg atoms

P. Pillet, V. M. Akulin, D. Comparat +3 more

Jan 1, 19980 citations

Ion-neutral chemical reactions between ultracold localized ions and neutral molecules with single-particle resolution

Bernhard Roth, Peter Blythe, H. Wenz +2 more

Chemical reactions between ultracold $^{9}\mathrm{Be}^{+}$ ions and room-temperature molecular hydrogen isotopomers and between ultracold ${\mathrm{H}}_{3}^{+}$ ions and room-temperature ${\mathrm{O}}_{2}$ have been studied in a laser-cooling ion trap apparatus. For small Coulomb crystals of beryllium ions, reactions can be followed at the single-ion level. We demonstrate characterization of a chemical reaction in which neither one of the reactants nor the product is directly detectable. In this case molecular dynamics simulations were used for the determination of ion numbers from images of the $^{9}\mathrm{Be}^{+}$ ion ensemble. The observed reaction rates are in agreement with the Langevin ion-neutral reaction theory.Chemical reactions between ultracold $^{9}\mathrm{Be}^{+}$ ions and room-temperature molecular hydrogen isotopomers and between ultracold ${\mathrm{H}}_{3}^{+}$ ions and room-temperature ${\mathrm{O}}_{2}$ have been studied in a laser-cooling ion trap apparatus. For small Coulomb crystals of beryllium ions, reactions can be followed at the single-ion level. We demonstrate characterization of a chemical reaction in which neither one of the reactants nor the product is directly detectable. In this case molecular dynamics simulations were used for the determination of ion numbers from images of the $^{9}\mathrm{Be}^{+}$ ion ensemble. The observed reaction rates are in agreement with the Langevin ion-neutral reaction theory.

Physical Review AApr 19, 200680 citations

Ultracold neutral plasmas and Rydberg gases

Thomas Pattard, Thomas Pohl, Jan Michael Rost

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and AtomsApr 26, 20051 citation

Chemical reactions between ultracold

^{9}\mathrm{Be}^{+}

ions and room-temperature molecular hydrogen isotopomers and between ultracold

{\mathrm{H}}_{3}^{+}

ions and room-temperature

{\mathrm{O}}_{2}

have been studied in a laser-cooling ion trap apparatus. For small Coulomb crystals of beryllium ions, reactions can be followed at the single-ion level. We demonstrate characterization of a chemical reaction in which neither one of the reactants nor the product is directly detectable. In this case molecular dynamics simulations were used for the determination of ion numbers from images of the

^{9}\mathrm{Be}^{+}

ion ensemble. The observed reaction rates are in agreement with the Langevin ion-neutral reaction theory.