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Nature Communications 9(1), 2259 (2018). doi:10.1038/s41467-018-04740-5, The toolbox for imaging molecules is well-equipped today. Some techniques visualize the geometrical structure, others the electron density or electron orbitals. Molecules are many-body systems for which the correlation between the constituents is decisive and the spatial and the momentum distribution of one electron depends on those of the other electrons and the nuclei. Such correlations have escaped direct observation by imaging techniques so far. Here, we implement an imaging scheme which visualizes correlations between electrons by coincident detection of the reaction fragments after high energy photofragmentation. With this technique, we examine the H2 two-electron wave function in which electron–electron correlation beyond the mean-field level is prominent. We visualize the dependence of the wave function on the internuclear distance. High energy photoelectrons are shown to be a powerful tool for molecular imaging. Our study paves the way for future time resolved correlation imaging at FELs and laser based X-ray sources., Published by Nature Publishing Group UK, [London]

Radiation damage to living tissue stems not only from primary ionizing particles but to a substantial fraction from the dissociative attachment of secondary electrons with energies below the ionization threshold. We show that the emission yield of those low energy electrons increases dramatically in ion–atom collisions depending on whether or not the target atoms are isolated or embedded in an environment. Only when the atom that has been ionized and excited by the primary particle impact is in immediate proximity of another atom is a fragmentation route known as interatomic Coulombic decay (ICD) enabled. This leads to the emission of a low energy electron. Over the past decade ICD was explored in several experiments following photoionization. Most recent results show its observation even in water clusters. Here we show the quantitative role of ICD for the production of low energy electrons by ion impact, thus approaching a scenario closer to that of radiation damage by alpha particles: We choose ion energies on the maximum of the Bragg peak where energy is most efficiently deposited in tissue. We compare the electron production after colliding He + ions on isolated Ne atoms and on Ne dimers (Ne 2 ). In the latter case the Ne atom impacted is surrounded by a most simple environment already opening ICD as a deexcitation channel. As a consequence, we find a dramatically enhanced low energy electron yield. The results suggest that ICD may have a significant influence on cell survival after exposure to ionizing radiation.

The generalizations that fusion would be safer than fission, involve no dangerous radioactive materials, and rely on a cheap and plentiful fuel are potentially true. But it is pointed out that the type of fusion machine that the U.S. program is developing will deliver only some of these advantages. A gap is developing between what the fusion program appears to promise and what it is most likely to deliver. Fusion power would not be infinitely abundant, because the present reactors rely on a fuel cycle that must have lithium, and lithium is not particularly more abundant than the /sup 238/U that would fuel the breeder reactor. Fusion power would not be free of radioactive gases because the lithium would be used to breed tritium--a gas more benign than fission products but one that is hard to contain. The fusion reactor would not be free of waste disposal problems, even though the ''spent fuel'' would be nonradioactive, because the burning of the fuel would produce approximately four times as many neutrons as a fission reactor, and such a neutron flux would make all the structural materials of the reactor intensely radioactive--one estimate of the waste disposal problem is at least 250more » tons of material every year from each reactor. Finally, fusion power would not be cheap. The greatest potential advantages of fusion occur with advanced fuel cycles which include deuterium with deuterium; deuterium with helium-3; helium-3 with helium-3; and hydrogen with boron. Fusion with these fuels could be a clean process, but most research is directed toward fusion of deuterium and tritium. The funding of the program in the U.S. has seen the magnetic fusion budget exploding from $38 million in 1973 to $279 million in 1977. A second article will clarify the properties of various types of fusion reactors. (MCW)« less

The role of laboratories and research centers, never fully defined by ERDA, has been reviewed by DOE officials, who indicate a gradual change in future administrative procedures is likely. Reorganization into a new department has changed reporting procedures and added new ways to monitor laboratory work. This has raised concerns that the laboratories will lose much of their past economic and program autonomy, which some critics felt were too lacking in competitive bidding and too ambitious. Future changes are expected to include more specific energy objectives for each facility and a resolution of whether the labs should be centers of excellence only or should interact as consultants and managers with outside agencies and contractors. The laboratories are grouped under solar research, weapons, energy research, nuclear fission and fusion development, basic research, and multipurpose according to their present emphasis. They are expected to remain at the same size (60,000 employees) and will not enlarge at the expense of university research.

The hybrid reactor employing fusion-fission reactions is discussed from technological and economic viewpoints. The hybrid concept as used with mirror machines and tokamaks is reviewed. Some advantages and disadvantages of using the hybrid system for breeding fissionable fuels are given. (MOW)

The breeder reactor programs in European countries, particularly the well-advanced French program, are reviewed.

A case is made that too much emphasis is placed on storage in connection with the use of solar energy. At present, any solar input is of value and only a small perturbation on the nation's energy picture. The use of hydroelectric installations as solar backup is discussed. Wind energy is described as suitable for winter-peaking utilities. Reliability through grid connection and storage research for the long term are discussed. (MHR)

The energy source in these galaxies will be shown to be a black hole, I think, even though it may take 100 years before we have proven it .—MARTIN REES, at the Institute of Astronomy in Cambridge, England I think it will take 1000 years and we may very well be on the wrong track. These [black hole] models are getting into the textbooks now, but there is never anything testable and people are working on smaller and smaller pieces of the problem .— GEOFFREY BURBIDGE, at the Univeristy of California, San Diego, and soon to assume the post of head of the Kitt Peak National Observatory in Tucson, Arizona REES: I agree, but I would argue that the way we are going about it is the most productive approach, even though the modelers may be getting the illusory satisfaction of a Ptolomean theorist who adds another epicycle . BURBRIDGE: I9m glad to hear you say that, Martin. The trouble is that so many people take these things more seriously than you do .