Rotational structures of long-range diatomic molecules

We present a systematic understanding of the rotational structure of a long-range (vibrationally highly-excited) diatomic molecule. For example, we show that depending on a quantum defect, the least-bound vibrational state of a diatomic molecule with $-C_n/r^n$ ($n>2$) asymptotic interaction can have only 1, 2, and up to a maximum of $n-2$ rotational states. A classification scheme of diatomic molecules is proposed, in which each class has a distinctive rotational structure and corresponds to different atom-atom scattering properties above the dissociation limit.Comment: 8 page

Universal properties in ultracold ion-atom interactions

We present some of the universal properties in ion-atom interaction derived from a newly formulated quantum-defect theory for $-1/r^4$ type of long-range interactions. For bound states, we present the universal bound spectrum, namely the equivalent of the Rydberg formula, for ion-atom systems. For scattering, we introduce the concept of universal resonance spectrum to give a systematic understanding of many resonances present in ion-atom scattering. The theory further provides a method for an accurate spectroscopic determination of the atomic polarizability. It also suggests the existence of atom-like molecules, in which multiple atoms orbit around a heavy ion.Comment: 4 pages, 2 figure

Influence of Heavy Quark Recombination on the Nucleon Strangeness Asymmetry

The nucleon strange and anti-strange distribution asymmetry is an important issue in the study of the nucleon structure. In this work, we show that the heavy quark recombination processes from a perturbative QCD picture can give a sizable influence on the measurement of the nucleon strangeness asymmetry from charged-current charm production processes, such as the CCFR and NuTeV dimuon measurements. When the influence of heavy quark recombination is considered, a positive effective $\delta S^-_{\mathrm{HR}}$ should be added to the initially extracted strangeness asymmetry $S^-\equiv\int dx[s(x)-\bar s(x)]x$, supporting the strangeness asymmetry $S^-$ being positive, which is helpful to explain the NuTeV anomaly within the framework of the standard model.Comment: 5 latex pages, 2 figure

Simple Theoretical Models for Resonant Cold Atom Interactions

Magnetically tunable scattering resonances have been used with great success for precise control of s-wave scattering lengths in ultracold atomic collisions. We describe relatively simple yet quite powerful analytic treatments of such resonances based on the analytic properties of the van der Waals long range potential. This theory can be used to characterize a number of properties of specific resonances that have been used successfully in various experiments with $^{87}$Rb, $^{85}$Rb, $^{40}$K, and $^{6}$Li. Optical Feshbach resonances are also possible and may be practical with narrow intercombination line photoassociative transitions in species like Sr and Yb.Comment: To be published in the Proceedings of the 20th International Conference on Atomic Physics, held in Innsbruck, Austria, July 200