Quantum ricochets: surface capture, release and energy loss of fast ions hitting a polar surface at grazing incidence

A diffraction mechanism is proposed for the capture, multiple bouncing and final escape of a fast ion (keV) impinging on the surface of a polarizable material at grazing incidence. Capture and escape are effected by elastic quantum diffraction consisting of the exchange of a parallel surface wave vector G= 2p/ a between the ion parallel momentum and the surface periodic potential of period a. Diffraction- assisted capture becomes possible for glancing angles F smaller than a critical value given by Fc 2- 2./ a-| Vim|/ E, where E is the kinetic energy of the ion,. = h/ Mv its de Broglie wavelength and Vim its average electronic image potential at the distance from the surface where diffraction takes place. For F< Fc, the ion can fall into a selected capture state in the quasi- continuous spectrum of its image potential and execute one or several ricochets before being released by the time reversed diffraction process. The capture, ricochet and escape are accompanied by a large, periodic energy loss of several tens of eV in the forward motion caused by the coherent emission of a giant number of quanta h. of Fuchs- Kliewer surface phonons characteristic of the polar material. An analytical calculation of the energy loss spectrum, based on the proposed diffraction process and using a model ion-phonon coupling developed earlier (Lucas et al 2013 J. Phys.: Condens. Matter 25 355009), is presented, which fully explains the experimental spectrum of Villette et al (2000 Phys. Rev. Lett. 85 3137) for Ne+ ions ricocheting on a LiF(001) surface.

Announcing the release of FishBase 96

FishBase is a computerized encyclopedia of fishes developed at International Center for Living Aquatic Resources Management (ICLARM) with the support of the European Commission and in collaboration with a large number of institutions throughout the world, notably FAO, and available since 1995 as CD-ROM. Major improvements since version 1.2 have now allowed for the release of FishBase 96, whose name indicates the intention to update FishBase annually. Some of the major improvements of FishBase 96 are: (a) 3,000 more species (total 15,000) and 3,000 more pictures (total 9,000); (b) complete marine checklists for 48 countries, and freshwater checklists for 60 countries; (c) a new user module to document local knowledge of fishes; (d) a stand-alone glossary defining 2,500 ichthyological and related terms; (e) new databases on brain weights (from R. Beauchot and colleagues at the University of Paris VII), on ciguatera (from P. Dalzell, South Pacific Commission, Noumea), and on recruitment (from R.A. Myers and colleagues at the Department of Fisheries and Oceans, St. John's); and (f) new graphs to display quantitative data: through time series, pie charts and bivariate plots. As before, FishBase is available free to collaborators, for US$50 as update to registered users of previous versions, and for US$95 for new users.

Announcing the release of FiSAT (version 1.0)

A brief description of the origin, "philosophy", and key features of FiSAT (FAO-ICLARM Stock Assessment Tools), the joint FAO-ICLARM software is given, along with information on its distribution and maintenance.

Longline-caught blue shark (Prionace glauca): factors affecting the numbers available for live release*

The blue shark (Prionace glauca) is an oceanic species that occurs in temperate and tropical waters around the globe (Robins and Ray, 1986). This species is a major bycatch of pelagic longline fleets that operate to supply the world’s growing demand for tunas and swordfish (Xiphias gladius) (Stevens, 1992; Bailey et al., 1996; Francis, 1998; Francis et al., 2001; Macias and de la Serna, 2002); numerically, the blue shark is the top nontarget species captured by the U.S. longline pelagic Atlantic fleet (Beerkircher et al.

Life after Catch and Release

Since 1988 regulations have required U.S. longline fishermen to release all Atlantic white marlin, Tetrapturus albidus. By the late 1990’s, approximately 99% of Atlantic white marlin caught by U.S. recreational fishermen were released. Recent studies using PSAT technology indicate that not all released fish survive and that a minor change in hook type, 0–5° offset circle hooks rather than straight-shank “J” hooks, may have a profound effect on post release mortality. Beginning in 2004, sea turtle mitigation measures have required U.S. longline fishermen to use circle hooks. Estimates of total catch, releases, and post release mortality of Atlantic white marlin caught by U.S. recreational fishermen were made in order to evaluate the potential reduction in mortality that may be realized by requiring the use of circle hooks rather than straight-shank “J” hooks by U.S. recreational fishermen. These estimates were compared to estimates of Atlantic white marlin caught by the U.S. longline fishery