Rate limit for photoassociation of a Bose-Einstein condensate

We simulate numerically the photodissociation of molecules into noncondensate atom pairs that accompanies photoassociation of an atomic Bose-Einstein condensate into a molecular condensate. Such rogue photodissociation sets a limit on the achievable rate of photoassociation. Given the atom density \rho and mass m, the limit is approximately 6\hbar\rho^{2/3}/m. At low temperatures this is a more stringent restriction than the unitary limit of scattering theory.Comment: 5 pgs, 18 refs., 3 figs., submitted to Phys. Rev. Let

On the road to Enlighten-ment: establishing an institutional repository service for the University of Glasgow

Purpose – The purpose of this paper is to chart the development and growth of open access and institutional repositories at the University of Glasgow, Scotland from initial work in 2001 to the University's recently launched service, Enlighten. The University of Glasgow is a signatory to the Scottish Open Access Declaration and recently released a statement on Open Access.<p></p> Design/methodology/approach – The study will focus on the key lessons learned through a twin track approach of advocacy and service development during the DAEDALUS Project (2002-2005) and the transition of that work to a University service called Enlighten. This service includes a repository for published and peer-reviewed papers which has now had over 2 million hits and over 270,000 PDF downloads since it was established in February 2004.<p></p> Findings – The paper reveals the lessons learned by the Library and the project team. It also identifies the range of issues which must be addressed in the successful implementation of a repository and its transition to a production service. These include the development of content policies, copyright clearance and the cultural change necessary to populate a repository service. These challenges have and continue to be addressed by the repository team at the University of Glasgow.<p></p> Originality/value – This paper provides details of the lessons learned in the practical experience of setting up an institutional repository and ensuring its transition to a full and supported University service. It will be of particular interest to institutions implementing a repository or running a pilot service.<p></p&gt

Sub-Natural-Linewidth Quantum Interference Features Observed in Photoassociation of a Thermal Gas

By driving photoassociation transitions we form electronically excited molecules (Na$_2^*$) from ultra-cold (50-300 $\mu$K) Na atoms. Using a second laser to drive transitions from the excited state to a level in the molecular ground state, we are able to split the photoassociation line and observe features with a width smaller than the natural linewidth of the excited molecular state. The quantum interference which gives rise to this effect is analogous to that which leads to electromagnetically induced transparency in three level atomic $\Lambda$ systems, but here one of the ground states is a pair of free atoms while the other is a bound molecule. The linewidth is limited primarily by the finite temperature of the atoms.Comment: 4 pages, 5 figure

The incidence, severity, timing and circadian variation of hypophosphataemia in Glasgow Royal Infirmary Intensive Care Unit [poster]

No abstract available

Fully anharmonic infrared cascade spectra of polycyclic aromatic hydrocarbons

The infrared (IR) emission of polycyclic aromatic hydrocarbons (PAHs) permeates our universe; astronomers have detected the IR signatures of PAHs around many interstellar objects. The IR emission of interstellar PAHs differs from their emission as seen under conditions on Earth, as they emit through a collisionless cascade down through their excited vibrational states from high internal energies. The difficulty in reproducing interstellar conditions in the laboratory results in a reliance on theoretical techniques. However, the size and complexity of PAHs requires careful consideration when producing the theoretical spectra. In this work we outline the theoretical methods necessary to lead to a fully theoretical IR cascade spectra of PAHs including: an anharmonic second order vibrational perturbation theory (VPT2) treatment; the inclusion of Fermi resonances through polyads; and the calculation of anharmonic temperature band shifts and broadenings (including resonances) through a Wang--Landau approach. We also suggest a simplified scheme to calculate vibrational emission spectra that retains the essential characteristics of the full IR cascade treatment and can directly transform low temperature absorption spectra in IR cascade spectra. Additionally we show that past astronomical models were in error in assuming a 15 cm$^{-1}$ correction was needed to account for anharmonic emission effects

Feshbach resonances and collapsing Bose-Einstein condensates

We investigate the quantum state of burst atoms seen in the recent Rb-85 experiments at JILA. We show that the presence of a resonance scattering state can lead to a pairing instability generating an outflow of atoms with energy comparable to that observed. A resonance effective field theory is used to study this dynamical process in an inhomogeneous system with spherical symmetry

Superposition of macroscopic numbers of atoms and molecules

We theoretically examine photoassociation of a non-ideal Bose-Einstein condensate, focusing on evidence for a macroscopic superposition of atoms and molecules. This problem raises an interest because, rather than two states of a given object, an atom-molecule system is a seemingly impossible macroscopic superposition of different objects. Nevertheless, photoassociation enables coherent intraparticle conversion, and we thereby propose a viable scheme for creating a superposition of a macroscopic number of atoms with a macroscopic number of molecules.Comment: 4 pages, 2 figs, to appear in Phys. Rev. Let