Classical Evolution of Quantum Elliptic States

The hydrogen atom in weak external fields is a very accurate model for the multiphoton excitation of ultrastable high angular momentum Rydberg states, a process which classical mechanics describes with astonishing precision. In this paper we show that the simplest treatment of the intramanifold dynamics of a hydrogenic electron in external fields is based on the elliptic states of the hydrogen atom, i.e., the coherent states of SO(4), which is the dynamical symmetry group of the Kepler problem. Moreover, we also show that classical perturbation theory yields the {\it exact} evolution in time of these quantum states, and so we explain the surprising match between purely classical perturbative calculations and experiments. Finally, as a first application, we propose a fast method for the excitation of circular states; these are ultrastable hydrogenic eigenstates which have maximum total angular momentum and also maximum projection of the angular momentum along a fixed direction. %Comment: 8 Pages, 2 Figures. Accepted for publication in Phys. Rev.

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

TRY plant trait database – enhanced coverage and open access

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

Studies of autoionizing states relevant to dielectronic recombination

In the past year we have focused most of our effort on the study of the 3pnl autoionizing states of Mg. Specifically, we have measured the angular distributions of electrons ejected from these states, we have carried out theoretical analyses of the experimentally determined angular distributions, and we have also made measurements of the autoionization rates of Mg 3pnk Stark states in electric fields. Finally, we have recorded the spectra of the autoionizing Ba 6pnk Stark states with very high optical powers to see the fine details in the wings of the spectra. Each of these activities is described in more detail in the ensuing paragraphs

FORCED AUTOIONIZATION OF THE Ba 5d7d STATE

Nous avons fait l'étude de l'interaction entre l'état 5d7d 1D2 situé à 200 cm-1 en dessous de la première limite d'ionisation du barium avec la série de Rydberg 6snd. Nous décrivons l'étude de l'interaction de l'état 5d7d avec le continuum Stark produit par des champs électriques de 5 kV/cm.We report the study of the interaction of the Ba 5d7d 1D2 state lying 200 cm-1 below the first ionization limit with the 6snd Rydberg series in which it is embedded. Specifically we describe the study of the interaction of the 5d7d state with the Stark continuum produced by electric fields of ~ 5 kV/cm

Dipole-dipole-coupled double-Rydberg molecules

10.1103/PhysRevA.86.031401Physical Review A - Atomic, Molecular, and Optical Physics863-PLRA