Collision photography: polarization imaging of atom-molecule collisions

We report differential scattering experiments on the laser excitation of Na+Mcollision pairs with M=N₂, CO, C₂H₂, and CO₂. The collision event is probed by the laser polarization revealing geometric and electronic properties of the collision pair. The experimental data are compared to the results of a Monte Carlo trajectory simulation using ab initio quantum chemical data.Financial support from the Deutsche Forschungsgemeinschaft and the Schweizerischer Nationalfond (Project No. 20- 065290.01) is gratefully acknowledged

Optimization of Generalized Multichannel Quantum Defect reference functions for Feshbach resonance characterization

This work stresses the importance of the choice of the set of reference functions in the Generalized Multichannel Quantum Defect Theory to analyze the location and the width of Feshbach resonance occurring in collisional cross-sections. This is illustrated on the photoassociation of cold rubidium atom pairs, which is also modeled using the Mapped Fourier Grid Hamiltonian method combined with an optical potential. The specificity of the present example lies in a high density of quasi-bound states (closed channel) interacting with a dissociation continuum (open channel). We demonstrate that the optimization of the reference functions leads to quantum defects with a weak energy dependence across the relevant energy threshold. The main result of our paper is that the agreement between the both theoretical approaches is achieved only if optimized reference functions are used.Comment: submitte to Journal of Physics

IRIS: Efficient Visualization, Data Analysis and Experiment Management for Wireless Sensor Networks

The design of ubiquitous computing environments is challenging, mainly due to the unforeseeable impact of real-world environments on the system performance. A crucial step to validate the behavior of these systems is to perform in-field experiments under various conditions. We introduce IRIS, an experiment management and data processing tool allowing the definition of arbitrary complex data analysis applications. While focusing on Wireless Sensor Networks, IRIS supports the seamless integration of heterogeneous data gathering technologies. The resulting flexibility and extensibility enable the definition of various services, from experiment management and performance evaluation to user-specific applications and visualization. IRIS demonstrated its effectiveness in three real-life use cases, offering a valuable support for in-field experimentation and development of customized applications for interfacing the end user with the system

Large-Scale Selective Sweep among Segregation Distorter Chromosomes in African Populations of Drosophila melanogaster

Segregation Distorter (SD) is a selfish, coadapted gene complex on chromosome 2 of Drosophila melanogaster that strongly distorts Mendelian transmission; heterozygous SD/SD+ males sire almost exclusively SD-bearing progeny. Fifty years of genetic, molecular, and theory work have made SD one of the best-characterized meiotic drive systems, but surprisingly the details of its evolutionary origins and population dynamics remain unclear. Earlier analyses suggested that the SD system arose recently in the Mediterranean basin and then spread to a low, stable equilibrium frequency (1–5%) in most natural populations worldwide. In this report, we show, first, that SD chromosomes occur in populations in sub-Saharan Africa, the ancestral range of D. melanogaster, at a similarly low frequency (∼2%), providing evidence for the robustness of its equilibrium frequency but raising doubts about the Mediterranean-origins hypothesis. Second, our genetic analyses reveal two kinds of SD chromosomes in Africa: inversion-free SD chromosomes with little or no transmission advantage; and an African-endemic inversion-bearing SD chromosome, SD-Mal, with a perfect transmission advantage. Third, our population genetic analyses show that SD-Mal chromosomes swept across the African continent very recently, causing linkage disequilibrium and an absence of variability over 39% of the length of the second chromosome. Thus, despite a seemingly stable equilibrium frequency, SD chromosomes continue to evolve, to compete with one another, or evade suppressors in the genome

WHAT DO WE MEAN BY "ELECTRONIC STRUCTURE"?

Author Institution: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139; Laboratoire Aim$\acute{e}$ Cotton du CNRS, Universit$\acute{e}$ de Paris Sud, B$\hat{a}$timent 505, F-91405, Orsay, France; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139A large and diverse set of spectroscopic data for the CaF molecule has been used to determine the parameters of an s$\sim$p$\sim$d$\sim$f quantum defect matrix and its derivatives with respect to energy and internuclear distance, $\mu$(E,R). The result is a complete description of the 10 Rydberg series (four $\Sigma$, three $\Pi$, two $\Delta$, and one $\Phi$) of CaF, each consisting of an infinite number of discrete states plus an associated ionization continuum. The quantum defect matrix may be converted into ten R-dependent eigenquantum defect functions, which describe the infinite series of potential energy curves and all the nonadiabatic interactions among them. The E dependences of these eigenquantum defect functions describe how the potential curves evolve as one goes from the lowest member (terminus state) of the series, where the Rydberg electron interacts most strongly with the not-round and chemically inhomogeneous ion-core, to the nearly-bare ion-core, where the electron$\leftrightarrow$ion interaction is of a predominantly long-range rather than chemical nature. The E-dependent shapes of the eigenquantum defect curves reveal global features of the electronic structure, such as direct and induced avoided crossings, that would not be evident in a state-by-state or even a series-by-series description. The principal irregularities appear to be due to exclusion of one $\Sigma$ and one $\Pi$ repulsive state, terminus states of series converging to excited states of the CaF$^+$ ion core, from the quantum defect matrix fit model

MULTICHANNEL QUANTUM DEFECT THEORY OF THE FORMYL RADICAL

Author Institution: Department of Chemistry and Physics, Augusta State University; Department of Chemistry, Purdue University; Department of Chemistry, National University of Ireland; Laboratoire de Photophysique Molecular du CNRS, Universite Paris SudThe high Rydberg states of the formyl radical (HCO) have been examined in great detail by means of double-resonance spectroscopy of vibrationally autoionizing states. Simulations utilizing the Rydberg formula have described these states in terms of a phenomological quantum defect ($\delta$). We have used these assignments as a guide in applying the multichannel quantum defect theory (MQDT) to HCO. The current calculations include intensity as well as energy considerations, and will serve as a further guide toward the development of a complete polyatomic MQDT formalism