Number 203, November 17, 1994 by Phillip F. Schewe and Ben Stein LIGHT EMISSION IS MAPPED WITH ATOMIC RESOLUTION. The old rule that optical microscopy cannot achieve a spatial resolution much better than the wavelength of the light used can be surmounted by positioning the light source very close to the sample. Such "near-field" microscopes have in the past few years achieved lateral resolutions of 30 angstroms. Scientists at the University of Lausanne and IBM Zurich in Switzerland have now done better than that. They use a scanning tunneling microscope (STM) to image the gold surface; the sample was mounted at such an angle to the STM probe as to present a sort of grating, with a periodicity of 8.16 angstroms. But while they acquire a topographical record of the gold surface, the Swiss physicists also use the STM probe tip to induce the emission of photons from the surface atoms. This light is detected by a photomultiplier. Because the light emission is so sensitive to the tip- sample interaction and because the position of the tip can be controlled with picometer precision, the resultant "photon map" of the gold surface (or at least a one-dimensional slice) has an atomic resolution comparable to the STM topographical map. (R. Berndt et al., Physical Review Letters, 2 Jan. 95) ATOMIC LONG JUMP. When a metal atom is put down on a crystal surface the atom will move about. It was thought that the atom (referred to as an "adatom") would randomly migrate from one binding site to an adjacent site. Experiments at the University of Illinois with isolated palladium atoms on a tungsten substrate have shown that an adatom can occasionally jump to as far as two or three sites away. The mechanism for these long jumps is not yet known. (Donna Cowell Senft and Gert Ehrlich, Physical Review Letters, upcoming article.) INERTIAL-CONFINEMENT FUSION RESEARCH at Livermore has partly come out from behind a cover of secrecy. In a series of four papers in Physical Review Letters, scientists at Livermore's Nova laser facility have described the state of their art. Nova shoots 10 beams of ultraviolet light (at a wavelength of 350 nm and a total peak power of 30 TW) into a uranium reaction vessel (2.5 mm long), where the energy is converted into x rays which converge on a tiny deuterium-tritium fuel capsule, causing fusion reactions to begin. So far temperatures above 1 million K have been achieved. The Livermore scientists and their Los Alamos collaborators believe that their experimental approach can be scaled up to the level needed for self-sustained fusion. The recently-announced, billion-dollar National Ignition Facility (NIF) is designed to do exactly that. (Four articles in Physical Review Letters, 24 October 1994.) TITAN MAY HAVE OCEANS. New observations by the Hubble Space Telescope, reported by Peter Smith of the University of Arizona at a recent astronomy meeting in Bethesda, Maryland, reveal several light and dark patches on the surface of Saturn's large moon. One continent-sized bright patch, for instance, may be a block of water ice and ammonia ice, while dark areas may be hydrocarbon oceans. Ambiguities in interpreting the observations (made at near-infrared wavelengths) come from the possibility that the patches might be indicative of features in Titan's hazy atmosphere rather than of oceans on the surface. (Science News, 12 November 1994.)