Detection Techniques for Trapped Ions

Various techniques are used to detect the presence of charged particles stored in electromagnetic traps, their energy, their mass, or their internal states. Detection methods can rely on the variation of the number of trapped particles (destructive methods) or the use of the ion's interaction with electromagnetic radiation as a non-destructive tool to probe the trapped particles. This review gives an introduction into various methods, discussing the basic mode of operation completed by the description of recent realizations

How to Upscale The Kinetics of Complex Microsystems

The rate constants of chemical reactions are typically inferred from slopes and intersection points of observed concentration curves. In small systems that operate far below the thermodynamic limit, these concentration profiles become stochastic and such an inference is less straightforward. By using elements of queuing theory, we introduce a procedure for inferring (time dependent) kinetic parameters from microscopic observations that are given by molecular simulations of many simultaneously reacting species. We demonstrate that with this procedure it is possible to assimilate the results of molecular simulations in such a way that the latter become descriptive on the macroscopic scale. As an example, we upscale the kinetics of a molecular dynamics system that forms a complex molecular network. Incidentally, we report that the kinetic parameters of this system feature a peculiar time and temperature dependences, whereas the probability of a network strand to close a cycle follows a universal distribution

Scattering lengths of calcium and barium isotopes

We have calculated the s-wave scattering length of all the even isotopes of calcium (Ca) and barium (Ba), in order to investigate the prospect of Bose-Einstein condensation (BEC). For Ca we have used an accurate molecular potential based on detailed spectroscopic data. Our calculations show that Ca does not provide other isotopes alternative to the recently Bose condensed 40Ca that suffers strong losses because of a very large scattering length. For Ba we show by using a model potential that the even isotopes cover a broad range of scattering lengths, opening the possibility of BEC for at least one of the isotopes.Comment: 4 page

Quantum-State Controlled Penning Ionization Reactions between Ultracold Alkali and Metastable Helium Atoms

In an ultracold, optically trapped mixture of $^{87}$Rb and metastable triplet $^4$He atoms we have studied trap loss for different spin-state combinations, for which interspecies Penning ionization is the main two-body loss process. We observe long trapping lifetimes for the purely quartet spin-state combination, indicating strong suppression of Penning ionization loss by at least two orders of magnitude. For the other spin-mixtures we observe short lifetimes that depend linearly on the doublet character of the entrance channel. We compare the extracted loss rate coefficient with recent predictions of multichannel quantum-defect theory for reactive collisions involving a strong exothermic loss channel and find near-universal loss for doublet scattering. Our work demonstrates control of reactive collisions by internal atomic state preparation.Comment: 5 pages, 5 figures + Supplemental Material

Global nitrogen and phosphate in urban wastewater for the period 1970 to 2050

This paper presents estimates for global N and P emissions from sewage for the period 1970-2050 for the four Millennium Ecosystem Assessment scenarios. Using country-specific projections for population and economic growth, urbanization, development of sewage systems, and wastewater treatment installations, a rapid increase in global sewage emissions is predicted, from 6.4 Tg of N and 1.3 Tg of P per year in 2000 to 12.0-15.5 Tg of N and 2.4-3.1 Tg of P per year in 2050. While North America (strong increase), Oceania (moderate increase), Europe (decrease), and North Asia (decrease) show contrasting developments, in the developing countries, sewage N and P discharge will likely increase by a factor of 2.5 to 3.5 between 2000 and 2050. This is a combined effect of increasing population, urbanization, and development of sewage systems. Even in optimistic scenarios for the development of wastewater treatment systems, global N and P flows are not likely to declin