Universal relations for identical bosons from three-body physics

Systems consisting of identical bosons with a large scattering length satisfy universal relations determined by 2-body physics that are similar to those for fermions with two spin states. They require the momentum distribution to have a large-momentum 1/k(4) tail and the radio-frequency transition rate to have a high-frequency 1/ω(3/2) tail, both of which are proportional to the 2-body contact. Identical bosons also satisfy additional universal relations that are determined by 3-body physics and involve the 3-body contact, which measures the probability of 3 particles being very close together. The coefficients of the 3-body contact in the 1/k(5) tail of the momentum distribution and in the 1/ω(2) tail of the radio-frequency transition rate are log-periodic functions of k and ω that depend on the Efimov parameter.     

K promoted oxidation of Al and Ta

Core level and valence band photoemission have been used to study the response to oxygen exposure of potassium-precovered, polycrystalline aluminum and tantalum substrates. Deposition of potassium overlayers in the coverage regime from zero to one monolayer, results in an increase of the rate of oxygen uptake for both substrates. The increased oxygen uptake is, however, relatively stronger on aluminum. Correlated measurements of work function and oxygen uptake show that there is a correspondence between these two parameters for low K coverages, i.e., lower work function results in higher oxygen uptake. These results may be understood in terms of a model in which the alkali atoms are increasing the rate of dissociation of oxygen molecules at the surface, as well as lowering the barrier for oxygen penetration into the surface, through a reduction in the system work function.     

Clock shift in a strongly interacting two-dimensional Fermi gas

We derive universal relations for the rf spectroscopy of a two-dimensional Fermi gas consisting of two spin states interacting through an S-wave scattering length. The rf transition rate has a high-frequency tail that is proportional to the contact and displays logarithmic scaling violations, decreasing asymptotically like 1/(ω2ln2ω). Its coefficient is proportional to ln2'(a'(2D)/a(2D)), where a(2D) and a'(2D) are the two-dimensional scattering lengths associated with initial-state and final-state interactions. The clock shift is proportional to the contact and to ln(a'(2D)/a(2D)). If |ln(a'(2D)/a(2D))| > 1, the clock shift arises as a cancellation between much larger contributions proportional to ln2(a'(2D)/a(2D)) from bound-bound and bound-free rf transitions.