bluuebunny/crossref_metadata_2025 huggingface dataset:
Women in physics: unnecessary, injurious and out of place?
Authors: Kistiakowsky Vera
Published: April 2009

The subtitle for this article is taken from a Strindberg essay written at the end of the 19th century opposing the appointment of the mathematician, Sonia Kovalevsky, to a professorship at the University of Stockholm, in which he attempts to prove “as decidedly as that two and two make four, what a monstrosity is a woman who is a professor of mathematics, and how unnecessary, injurious and out of place she is”. It is certainly a much more extreme statement than anything likely to be voiced publicly today but it does vividly and tersely encapsulate many of the opinions that have been expressed to me in much more veiled and discursive form over the last ten years. Largely because of these continuing though muted attitudes I have accepted an invitation to write this article for PHYSICS TODAY. I will very briefly sketch the history of women's participation in physics as a background to the current situation and then discuss some statistical information about women physicists in the recent past and present in the United States. It will come as no surprise that the percentage of physicists who are women is small and that their employment patterns are different from those of men. I will discuss the possible reasons for this situation. Finally, I will comment briefly on recent changes and what expectations one may have for the future.
Earthquake at LLL hurts structures more than lasers
Authors: Lubkin Gloria B.
Published: April 2009

When the earthquake struck the Lawrence Livermore Laboratory laser-fusion facility on 24 January, most of the damage it inflicted was to the buildings and support facilities, according to John Emmett, who directs the program. Out of the $8 million in optical components in the two-armed Argus laser and 20-armed Shiva laser, only $13 000 worth of damage occured. Repair of the support equipment will cost $126 000, a figure that includes electrical and mechanical equipment and the expense of repositioning the laser and target frames. (The target frame, for instance, weighs 400 000 pounds and had to be jacked up and shifted back into place to ensure optimal alignment of beams.)
Statistical mechanics of simple fluids: beyond van der Waals
Authors: Lebowitz Joel L. , Waisman Eduardo M.
Published: April 2009

Dense fluids, defined to include both dense gases and liquids, have the reputation of being especially difficult to deal with theoretically. This reputation is not undeserved. Unlike dilute gases and crystalline solids, which can be thought of as deviants from well understood ideal states, the ideal gas and the ideal harmonic crystal, the dense fluid lies far from any recognizable landmark. This rules out the use of straightforward, convergent or asymptotic, expansions—the all-purpose tool of the theoretical physicist—and makes even the hardy wince.
Physics Today in China
Authors: Lubkin Gloria B.
Published: April 2009

When I landed in Peking one cold night last November I was warmly greeted by Kuan Wei-yen, a low-temperature physicist who runs Academia Sinica's Institute of Physics. It was the start of a three-week tour of the People's Republic of China as the guest of Academia Sinica, in which I met with Vice-Premier Fang Yi and other leading science officials, visited six physics institutes and five university physics departments.
Surface-enhanced Raman effect
Authors: Foerster Thomas von
Published: April 2009

A recently discovered and as yet incompletely understood effect promises to become an excellent tool for investigating molecules adsorbed onto metal surfaces. The effect consists of a spectacular enhancement—by factors of up to around 106—of Raman scattering by monolayers of molecules adsorbed onto microscopically rough metal surfaces (rough on a scale of 500–1000 Å). One of the most exciting prospects is that the effect will become a useful analytical tool for studying catalysis and other processes that take place on surfaces. As Elias Burstein, one of the early investigators in the field, put it, we are just learning how to put microscopic amplifiers onto metal surfaces.
Radioactive waste bound in crystals
Authors: Schwarzschild Bertram M.
Published: April 2009

Long-lived products of uranium fission such as strontium-90 and cesium-137, with half lives of about 30 years, cease to be a problem in reactor wastes after a few centuries. But the alpha-active transuranic actinides produced by transmutation in reactor fuel rods live much longer. Neptunium-237, plutonium-239, americium-241 and curium-246 have half lives ranging from five hundred to two million years. Although a waste disposal site would be no more radioactive after 500 years than a natural pitchblende ore deposit, it is widely felt that one should take reasonable precautions to keep these waste actinides out of the biosphere for hundreds of thousands of years.
The young Oppenheimer: letters and recollections
Authors: Smith Alice Kimball , Weiner Charles
Published: April 2009

A prominent physicist before World War II, J. Robert Oppenheimer became the wartime director of the Los Alamos nuclear weapons laboratory. After the war he became an influential adviser to the government on atomic energy, but fell from favor during the McCarthy era. This story has become the stuff of myth and drama. Here we would like to present glimpses of the less familiar Oppenheimer—learning, playing, making friends, doing physics, winning recognition—as yet unburdened by the actuality of the bomb, by fame and by public responsibilities.
Detecting art forgeries
Authors: Fleming Stuart
Published: April 2009

Art forgery is a complex subject; it has as much to do with the personality of the faker or the salesman who markets the spurious work as it has to do with the recapturing of some past technique or mood. And it is a subject that is still highly active today, despite the unquestionably improved art historical scholarship of recent decades: the controversy over the gold from Ziwiye, the stir caused by the forgery of Fragonard and Samuel Palmer, and the impact of the Beirut school's pressure-cast counterfeits of early English coinage—all headline-makers over the past five years—affirm that clearly enough.
Physics and the APS in 1979
Authors: Branscomb Lewis M.
Published: April 2009

We physicists are a diverse group. Some teach, some work in industry, others in national or other private laboratories. Our work ranges from basic to applied, and perhaps more important, many of us have exploited the power of physics to open up new fields of science, which then take on a disciplinary identity of their own. Physics is too useful and too interesting to exist in isolation from the mainstream of modern life. The work of physicists has done much to shape the world around us, and we have a major responsibility to be not only aware of the revolutionary effect of scientific ideas but to participate in the application of those ideas toward constructive purposes. We must do this, however nervous we may be about the corrosive effect of that mainstream on the principles we hold dear, principles that sustain the personal, intellectual and aesthetic rewards inherent in the practice of good physics. Indeed, only by active engagement in the affairs of society can we protect these principles and thus the health of our science and its value to future generations. This interplay will be my theme. But, first let me describe the state of The American Physical Society.
China emphasizes laser research
Authors: Lubkin Gloria B.
Published: April 2009

One of the eight scientific fields receiving special emphasis in the People's Republic of China these days is lasers. At the International Quantum Electronics Conference to be held in Boston this June, seven of the fifteen papers submitted from China were accepted. For the conference as a whole, 150 papers were accepted out of 450 submitted, suggesting that the Chinese are now competitive internationally.
Mercury data show no Sun shrinkage
Authors: Lubkin Gloria B.
Published: April 2009

Last year when John Eddy and Aram Boornazian reported evidence that the Sun has been contracting about 2 arc seconds per century, the announcement was greeted with excitement tempered by skepticism. Their evidence, reported at the American Astronomical Society meeting last June (PHYSICS TODAY, September 1979, page 17) and still not published, was obtained by analyzing measurements of the Sun's transit made at the Royal Greenwich Observatory (from 1836 to 1953) and the Naval Observatory (from 1864 to 1953). Now Irwin Shapiro of MIT has published an old analysis of 23 transits of the planet Mercury in front of the Sun in the period 1736–1973. He finds that the solar diameter cannot be decreasing more than 0.3 arc seconds per century, with a 90% confidence limit.
Thin-film formation
Authors: Vossen John L. , Kern Werner
Published: April 2009

The enormous number of successful applications of thin films for a large variety of scientific, engineering and industrial purposes is in large measure due to the rapidly increasing scientific understanding of the nature of the processes used to deposit thin films. Remarkable advances have been made, especially over the last decade, both in the understanding of older processes and in the development of new ones to satisfy new, and ever more sophisticated, needs. This special issue of PHYSICS TODAY includes representative articles on thin-film processes, analytic techniques and applications.
Analysis of thin films and interfaces
Authors: Poate John M. , Tu King-Ning
Published: April 2009

The preceding articles in this special issue amply demonstrate the crucial role that thin films play in present-day science and technology. These films can now be fabricated routinely and their application in advanced technologies is assured. To control the quality of the films and to measure their behavior we must develop techniques that can make measurements on minute quantities of material with dimensions of fractions of a micron. We need to determine the crystal structure, the chemical composition and the microstructure of the films. In the past five years or so, we have seen the realization of analytical techniques that give detailed information on thin-film structures, information that was not accessible with earlier analytic techniques.
Applications of metallurgical coatings
Authors: Bunshah Rointan F. , Mattox Donald M.
Published: April 2009

What do we mean by a “metallurgical coating?” A coating may be defined as a near-surface region having properties differing from the bulk of the material, and coatings may be desirable or even necessary for a variety of reasons including economics, unique properties or the engineering and design flexibility that can be obtained by separating the surface properties from the structural requirements. Metallurgy, of course, is the art and science of procuring, shaping, treating and use of metals; but when we study metallurgical coatings we are concerned not only with the physical and mechanical properties of the materials themselves but also with the interaction of materials with their environments and the substrates. Thus “metallurgical coatings” involves us with a broad spectrum of problems ranging from deformation properties, to chemical interactions, to solid-state properties.
Solid helium-3 is not as simple as we thought
Authors: Levi Barbara G.
Published: April 2009

Helium-3 has revealed yet another quirk in the complex pattern of its behavior at low temperatures. The latest surprise is that the nuclear spins in its magnetically ordered solid phase are not arranged according to the simplest symmetries one would associate with its underlying body-centered-cubic lattice. This conclusion comes from two simultaneous but independent nuclear magnetic resonance studies done by Douglas D. Osheroff, Michael C. Cross and Daniel S. Fisher at Bell Telephone Laboratories and by Dwight Adams, Erwin A. Schubert, Greg E. Haas and Donovan M. Bakalyar at the University of Florida (at Gainesville). Interpretation of the Bell Labs data is exceptionally clear because the experimenters there succeeded in growing a single crystal of solid He3 below its transition temperature to a magnetically ordered state. The two studies probe behavior at different regions of the applied magnetic field and thus complement one another.
Stable spin-polarized atomic hydrogen
Authors: Schwarzschild Bertram M.
Published: April 2009

The strong attraction between hydrogen atoms of opposite electron spin would seem to make it impossible to have stable monatomic hydrogen gas, except in interstellar space. But the force between hydrogen atoms of parallel spin is predominantly repulsive. Isaac Silvera and Jook Walraven of the University of Amsterdam have taken advantage of the absence of bound states for spin-polarized hydrogen to produce a monatomic hydrogen gas that showed no sign of reverting to ordinary H2 after almost an hour in a high magnetic field at low temperature, despite its very considerable density—more than 1016 atoms/cm3.
PEP stores electrons and positrons
Authors: Lubkin Gloria B.
Published: April 2009

PEP celebrated its first stored electron beam on 21 April. On 5 May both positron and electron beams were stored, each at 8 GeV; since then beam currents of 2 mA for electrons and 1.5 mA for positrons have been reached. PEP director John Rees explained that the currents were deliberately kept low to avoid the incoherent beam-beam limit. As commissioning continues, the PEP team will bring the beams to 15 GeV each, where peak performance is expected. The maximum design energy is 18 GeV/beam.
Solid-state physics in China
Authors: Lubkin Gloria B.
Published: April 2009

Materials research and electronic computers are two of the eight fields China has chosen to emphasize during the next several years. So it was not surprising that some of the most advanced research and development that I saw during my recent visit to China (PHYSICS TODAY, March, page 32) was related to solid-state physics and electronic circuitry.
Laue–Langevin Institute expands
Authors: Schwarzschild Bertram M.
Published: April 2009

The von Laue–Langevin Institute, at Grenoble in the French Alps, is getting its second wind. This much we are told by the appellation Deuxieme Souffle, the name given to the 104-million-franc renewal program recently approved by the steering committee of this joint French–German–British neutron-beam laboratory. The planned expansion of neutron sources and instrumentation should add significantly to the experimental capabilities of what is already the most powerful source of continuous neutron beams in Europe—and the leading source of cold and ultra-cold neutrons in the world.
Einstein's impact on theoretical physics
Authors: Yang Chen-Ning
Published: April 2009

There occurred in the early years of this century three conceptual revolutions that profoundly changed Man's understanding of the physical universe: the special theory of relativity (in 1905), the general theory of relativity (1915) and quantum mechanics (1925). Einstein personally was responsible for the first two of these revolutions, and influenced and helped to shape the third. But it is not about his work in these conceptual revolutions that I shall write here. Much has been written about that work already. Instead, I shall discuss, in general terms, Einstein's insights on the structure of theoretical physics and their relevance to the development of physics in the second half of this century. I shall divide the discussion into four sections which are, of course, very much related.
Do neutrinos oscillate from one variety to another?
Authors: Lubkin Gloria B.
Published: April 2009

As the concept of the neutrino has developed since the early 1930's, it has developed a split personality and put on weight. The neutrino is now thought to come in three varieties—electron neutrino, muon neutrino and tau neutrino. And a number of experiments are showing hints that a neutrino has a small mass and that it can oscillate from one variety to another. Taken alone, however, any individual experiment cannot be considered strong evidence of neutrino oscillations.
CERN hopes to finish LEP by 1986
Authors: Schwarzschild Bertram M.
Published: April 2009

If you thought a herd of bison grazing in the middle of the Fermilab accelerator was impressive, consider a colliding-beam accelerator whose electrons and positrons will circle more than a dozen villages in two countries. That is in fact the scale on which the Europeans hope to be doing high-energy physics by 1986.
The method of successive oscillatory fields
Authors: Ramsey Norman F.
Published: April 2009

In 1949 I was looking for a way to measure nuclear magnetic moments by the molecular-beam resonance method, but to do it more accurately than was possible with the arrangement developed by I. I. Rabi and his colleagues at Columbia University. The method I found was that of separated oscillatory fields, in which the single oscillating magnetic field in the center of a Rabi device is replaced by two oscillating fields at the entrance and exit, respectively, of the space in which the nuclear magnetic moments are to be investigated. During the 1950's this method became extensively used in the original form. In the same period more general applications of the method arose, and the principal extensions included:

▸ Use of relative phase shifts between the two oscillatory fields

▸ Extension generally to other resonance and spectroscopic devices, such as masers, which depend on either absorption or stimulated emission

▸ Separation of oscillatory fields in time instead of space

▸ Use of more than two successive oscillatory fields

▸ General variation of amplitudes and phases of the successive applied oscillatory fields.
Quarks, atoms, and the 1/N expansion
Authors: Witten Edward
Published: April 2009

Most particle physicists now believe that protons, neutrons, and other strongly interacting particles are built from more basic constituents known as “quarks” and “gluons,” which interact according to the rules of a relativistic quantum field theory known as “quantum chromodynamics.”
Garching shows stellarators may be good after all
Authors: Schwarzschild Bertram M.
Published: April 2009

Stellarators appear to be back in business. After a series of consistently disappointing results in the 1960's, Lyman Spitzer's scheme for plasma confinement in a toroidal fusion device was generally abandoned in the last decade by American magnetic-confinement researchers, in favor of the more promising tokamak concept.
Antiproton–proton colliders and Intermediate Bosons
Authors: Cline David , Rubbia Carlo
Published: April 2009

The development of particle accelerators in the 1920–30's was strongly influenced by the availability of intense sources of ions as well as the ability to shape magnetic fields and to produce high electric fields. Later, electron synchrotrons required intense electron sources. Still later the development of electron–positron colliding-beam machines required positron sources. At present CERN and Fermilab are developing intense sources of antiprotons and related beam-cooling techniques needed to make intense sources. We expect these antiproton sources to influence the development of future particle accelerators and storage rings just as profoundly as ion, electron and positron sources have in the past. One immediate use for the antiprotons is the creation of high-energy antiproton–proton colliders.
Unified theory of elementary-particle forces
Authors: Georgi Howard , Glashow Sheldon L.
Published: April 2009

The notion of what are the “elementary” or structureless constituents of matter keeps changing as we are able to probe smaller and smaller distances with higher and higher energies. As long as we were limited by the energy available in chemical processes, the elementary particles were atoms; later they were protons, neutrons and electrons; currently we can smash matter into pieces sufficiently fine that quarks and leptons appear to be the elementary consituents of matter.
Germanium detector sees galactic gamma-ray line
Authors: Rothenberg Marian S.
Published: April 2009

A two-day balloon flight over Alice Springs, Australia, has brought some good news for the budding field of gamma-ray line astronomy. The balloon carried a high-resolution germanium detector, which found a narrow 511-keV positron annihilation line coming from the direction of the Galactic center. Because positrons are produced in many of the high-energy processes believed to be occurring in the Galaxy—such as cosmic-ray induced interactions and explosive nucleosynthesis—the 511-keV annihilation is one of the most obvious gamma-ray lines to look for as evidence of these processes. Until these observations, described at the April meeting of The American Physical Society in Washington, D.C. and just published in the 1 October issue of Astrophysical Journal Letters, there had been no unambiguous evidence of a steady, nonsolar gamma-ray line.
Two groups plan for giant optical telescopes
Authors: Bennett Floyd Carse
Published: April 2009

Astronomers today are pushing existing optical telescopes to their limits: Better optical coatings, sophisticated microelectronics and computer control, and detector quantum efficiencies approaching unity make it possible to wring nearly the last photon of light-gathering capacity from present instruments. To improve optical telescopes still further, it appears, one must produce larger-aperture primaries.
Multiwire and drift proportional chambers
Authors: Charpak Georges
Published: April 2009

In some kinds of experiments, the accurate localization of ionizing particles is essential. Multiwire proportional chambers and drift chambers, first developed in the late 1960's, are now routine tools in such applications. Although the structure of these detectors is very simple, our understanding of them has evolved rapidly in recent years, as has the variety of modes in which they have been operated. Here we shall consider briefly the operation of these detectors. Then we can proceed to a discussion of the latest developments, which aim to obtain information on the reaction products of the most complex high-energy collisions, with the utmost accuracy and efficiency. (Detailed descriptions of the detectors and their properties can now be found abundantly in the literature, which is extensively reviewed in references 3 and 4.)
The Time Projection Chamber
Authors: Marx Jay N. , Nygren David R.
Published: April 2009

Progress in experimental high-energy physics is limited in practice by two complementary aspects: the types of beam particles available with useful intensities and energies, and the characteristics of the detection techniques available for measuring needed information about collisions of interest and their subsequent reaction products. Most impressively, advances in accelerator design over the last three decades have led to an increase in beam energies of nearly three orders of magnitude, and the advent of colliding-beam machines has brought a comparable increase to the center-of-mass energy available. The diversity of useful beam species has now grown to include essentially all known particles with lifetimes greater than 10−11 seconds.
Solar-neutrino hunters still seek explanation
Authors: Levi Barbara G.
Published: April 2009

More than ten years of painstaking measurements of the solar-neutrino flux have been summarized, and at least as many years of future experimentation have been previewed, in conference talks and in journal articles over the last year. At the Conference on the Status and Future of Solar-Neutrino Research held at Brookhaven National Laboratory in January, Raymond Davis Jr and his coworkers from Brookhaven presented a statistical average of the past eight years of measurements of the solar-neutrino flux. The value was 1.7 ± 0.4 SNU (one solar-neutrino unit = 10−36 captures per target atom per second), about one-third that predicted by the standard solar model (4.7 SNU). Unlike the first data that hinted at the unexpectedly low value, the current results have gained general acceptance because the careful refinements and checks in the intervening years have dispelled most doubts. No one knows whether the current discrepancy between theory and experiments reflects an inadequate understanding of the dynamics of the Sun's core or a lack of knowledge of some aspect of nuclear or neutrino physics (although there tends to be some mutual finger pointing!). To resolve the question, many research groups have advanced concepts for future experiments. Feasibility studies of these proposed experiments continue to be updated and debated.
Magnetism in one dimension
Authors: Birgeneau Robert J. , Shirane Gen
Published: April 2009

Not just biological phenomena but most physical phenomena as well become drastically altered or impossible in spaces of fewer than three dimensions. As is well known, the cooperative behavior of many-body systems depends very strongly on the coordination of the closely interacting particles and therefore on the number of spatial dimensions. As we shall see, not only does an examination of physics in fewer than three dimensions illuminate the familiar world of three dimensions, there are also real systems whose structure effectively reduces their dimensionality and for which, therefore, low-dimensional physics is a prerequisite. As a consequence, a considerable effort has been expended in explaining the properties of lower-dimensional and, especially, linear systems. During the last decade there has been a veritable explosion in the “one-dimensional” literature. In this article we would like to discuss in the context of magnetism some of the motivating factors for this explosion and the progress that has been achieved so far.
Tandem-mirror machines promise better efficiency
Authors: Scott John T.
Published: April 2009

A major problem with magnetic-mirror devices for plasma confinement has always been the leakage of particles out of the ends of the machine. An experiment now under construction at Lawrence Livermore Laboratory, known as the Tandem Mirror Experiment (TMX), proposes to turn this failing neatly to advantage by employing two mirror-pairs, one at each end of a long straight solenoid. Each pair of mirrors confines positive ions by minimum-B magnetic-field wells, and the excess positive charge that develops in these “end cells” confines ions within the solenoid. In other words, the two mirror pairs act as plugs for the ends of the solenoid. Calculations for a reactor based on this concept predict that, under appropriate neutral injection conditions, a plasma of a density and temperature sufficient for controlled fusion will build up in the solenoid. The purpose of the TMX experiment is to test the principles of the concept. Other tandem-mirror experiments are planned or already under construction at Novosibirsk in the Soviet Union, at the University of Tsukuba in Japan, and at the University of Wisconsin at Madison.
Visiting Physicists Program
Authors: Millman Sidney
Published: April 2009

I have a letter from a graduate student who writes “Many of us [students] are very ignorant as to the structure of research in industry.” Another graduate student writes, about industrial research in physics, “I [had] suspected that there is greater pressure to produce and a generally less interesting environment than in an academic setting.” It was to help counter these very prevalent attitudes that The American Physical Society set up its Visiting Physicists Program in 1973. In its current form the program arranges visits by physicists from industrial and national laboratories to university physics departments and visits by professors and their students to R&D laboratories, to improve the interaction between these two worlds. The success of this four-year-old program can be judged by its steady growth and by comments from those who have participated in visits, such as the two students quoted above. The first student's letter continues by praising the program for being both informative and interesting, and the second student, who had been suspicious of the R&D laboratories before his visit to one, writes “These feelings have been allayed by my visit… I am now much more favorably disposed toward the research environment at such institutions.”
Biomembrane phase transitions
Authors: Nagle John F. , Scott Hugh L.
Published: April 2009

Along with DNA and proteins, cell membranes are among the principal organizational structures of living matter. Over the past decade the study of cell membranes has become a focus of effort ranging from the very biologically oriented to the very physically oriented. One property that is especially appropriate for physical studies is the phase transition that occurs in many cell membranes.
New limit on constancy of velocity of light
Authors: Lubkin Gloria B.
Published: April 2009

Among today's physicists, it is doubtful that many would claim that the speed of light depends on the velocity of the source. But it is pleasing to know just how right Einstein's second postulate in the special theory of relativity is. Recently, by analyzing observations of pulsating x-ray sources in binary star systems, Kenneth Brecher of MIT has calculated a limit he believes is five orders of magnitude better than past verifications.
Patents: Another way to publish
Authors: Dann C. Marshall
Published: April 2009

Some scientists, including physicists, think that there is something rather crassly materialistic about being interested in patents, and that patents are usually given for clever trivialities. Edwin Land, the founder and chairman of Polaroid, who recently received his 500th patent and was at the same time inducted into the National Inventor's Hall of Fame, said on that occasion that “an inventor is thought of as an ingenious man who puts a date roller on the chicken so that each fresh egg will receive a date stamp.”
Steps toward the Hertzsprung–Russell Diagram
Authors: DeVorkin David H.
Published: April 2009

In the late nineteenth century, astronomers seeking to classify stars by their spectra using then-current concepts of stellar evolution found a temperature–luminosity plot that revolutionized the subject.
Gamma-ray lines: A new window to the Universe
Authors: Lingenfelter Richard E. , Ramaty Reuven
Published: April 2009

Gamma-ray lines are the signature of nuclear processes taking place at many astrophysical sites. The observation of line emission in the celestial gamma-ray spectrum, although a venture still in its infancy, is one of enormous potential, opening as it does a new and exciting window to the Universe. The potential for the extension of our knowledge of the Universe through celestial nuclear-line spectroscopy may match—or even exceed—that already achieved by extensive studies of the two other fundamental types of line emission, atomic and molecular. Because of their greater penetration, nuclear lines can be observed from processes and regions from which other lines can not.
Laser-fusion devices at Livermore and Rochester use Nd glass
Authors: Levi Barbara G.
Published: April 2009

Fusion research with solid-state lasers entered a higher-power regime recently as the Lawrence Livermore Laboratory began operating its 20-beam, 20–30 terawatt (1012 watts) neodymium–glass laser system. The design and current status of the facility were described by the associate director of Livermore, John L. Emmett, and others at the Conference on Laser and Electro-Optical Systems held in San Diego in February. After having successfully fired all twenty arms of the system at 10 kilojoules with a pulse of 1 nanosec, the Livermore group was changing the configuration for shorter (down to 0.1 ns) pulses, installing the final pieces of diagnostics and hardware, and aligning the lasers on a target in groups of five. A photograph of the target chamber appears on the cover of this issue of PHYSICS TODAY. The power of 1.7 TW attained by the first beam had confirmed hopes that all twenty beams would collectively reach the upper limit of the design power.
Panel promotes electron-beam studies of nucleus
Authors: Waff Craig B.
Published: April 2009

Noting new technical developments and consequent new opportunities for research, a panel has recommended increased funding over the next few years for the field of nuclear research using intermediate-energy electron accelerators. The Study Group on the Role of Electron Accelerators in US Medium Energy Nuclear Science, headed by Robert S. Livingston (Oak Ridge), has also recommended that the nuclear-physics community give serious consideration to the construction (beginning as early as 1981 or 1982) of a new national electron accelerator with a 100% duty cycle, energy of 1 to 2 GeV and electron-beam current of approximately 100 μA.
Why is iron magnetic?
Authors: Stearns Mary Beth
Published: April 2009

The unravelling of the origin of magnetism in iron, cobalt, nickel and their alloys has been a fascinating subject of study for many years. It is elusive because the structure of the valence electrons in the transition metals is very complex. Only in the last decade has there been a sufficient understanding of this structure to appreciate the crucial features of ferromagnetism. We now know the two conditions the electronic structure of a metal must satisfy for it to be a ferromagnet, and this understanding is helping us synthesize new magnetic alloys.
Rare-gas halide lasers
Authors: Ewing James J.
Published: April 2009

The rare-gas monohalides are simple diatomic molecules whose properties and emission spectra were essentially unknown as recently as four years ago. Now they are the active media for gas lasers that could provide overall electrical efficiency as high as 10%. These lasers operate in the ultraviolet and vacuum-ultraviolet spectral regions and are the first lasers outside the infrared region that appear to be scalable to high single-pulse energy (greater that 100 joules per pulse) with high average power and efficiency. Not surprisingly in light of the species' novelty and the laser's promised utility (for example, in photochemical-separation schemes), research and development in this area has grown remarkably since the first laser demonstration three years ago.
Sub-picosecond spectroscopy
Authors: Ippen Erich P. , Shank Charles V.
Published: April 2009

Ever since Man first became interested in movements and events that occurred too rapidly for his eye to follow, short flashes of light have been used to isolate moments of time. Each time shorter light pulses have become available, new areas of research have opened up, and new types of ultafast processes have become amenable to study. Spark photography can freeze the most rapid movement of macroscopic objects with flashes a tenth of a microsecond in duration. High-speed flashlamps and electronics play an important role in the study of fast photophysical and photochemical reactions with a resolution of a tenth of a nanosecond—10−10 sec. The last decade has seen dramatic advances in the development of short laser pulses and their application to the study of picosecond phenomena. Now, the extension of this technology into the sub-picosecond (10−13 sec) regime offers exciting possibilities for accurate studies of previously unresolved, ultrafast photoprocesses in physics, chemistry and biology. Investigations are being extended to such diverse and important topics as the vibrational dynamics of molecules and lattices, primary photobiological mechanisms and picosecond electronic processes in semiconductors.
Laser fusion
Authors: Stickley C. Martin
Published: April 2009

Laser-driven fusion is one approach to a long-term solution to the world's energy supply problems, based on a virtually inexhaustible fuel source, deuterium from water. It is also, along with magnetically confined fusion, one of the most difficult scientific tasks ever undertaken.
Ship hydrodynamics
Authors: Lafrance Pierre
Published: April 2009

For millenia Man has built surface vessels and used them to transport himself and his goods over water. Some appreciation for hydrodynamic forces is required to produce a functional vessel, and throughout history Man has had to rely on experience and empirical knowledge to guide his design efforts. Until recently, power for these ships has come from a limited number of sources: Sails were used to harness the winds, and men were persuaded to handle oars. However, winds tend to be unreliable, and human propulsion systems suffer from severe speed and endurance limitations. With the advent of mechanization and the discovery of new energy sources, higher speeds became attainable. With these, the effects of hydrodynamic forces become more pronounced, making it necessary to understand the patterns of water flow caused by ships to improve their performance.
Laser annealing shows promise for making p-n junctions
Authors: Leuchtag H. Richard
Published: April 2009

Ion implantation, a powerful technique for producing p–n junctions—the life-blood of solid-state electronics and photovoltaic solar cells—has run into snags, and now there is a promising new way to cut through these snags: laser annealing.
Fusion computer center expands at Livermore
Authors: Waff Craig B.
Published: April 2009

Groundbreaking for a new building to house the National Magnetic Fusion Energy Computer Center recently took place at Lawrence Livermore Laboratory. The $5-million, 44 000-square-foot facility is scheduled for completion in February 1979, and will house two large computers, a Cray-1 and a CDC 7600.
Heisenberg's first paper
Authors: Cassidy David C.
Published: April 2009

Werner Heisenberg had just celebrated his twentieth birthday when he presented his first paper for publication in 1921. This paper, a long and complex study entitled “On the Quantum Theory of Line Structure and of the Anomalous Zeeman Effects,” immediately placed its young author on the forefront of theoretical spectroscopy. “He understands everything,” Niels Bohr remarked. But, as often happens with brilliant first papers, its unique proposals were as controversial and perplexing as the phenomena they purported to explain. Figure 1 is a reproduction of part of the first page of this paper.
Research challenge: clean energy from coal
Authors: Cooper Bernard R.
Published: April 2009

The need for the use of coal as a source of energy presents an environmental problem of enormous scope and difficulty, and physicists can contribute much toward solving this problem. Both coal as a material and the technical processes employing coal present “dirty” problems. The fact is, however, that the complexities involved in this problem create possibilities and need for applied research of a high quality. For example, to minimize the pollution, recent developments often resort to indirect or elaborate means for extracting the energy content of coal.
The transition to turbulence
Authors: Swinney Harry L. , Gollub Jerry P.
Published: April 2009

Fluid flows have been studied systematically for more than a century and their equations of motion are well known, yet the transition from laminar flow to turbulent flow remains an enigma. The difficulty lies in the intractability of the nonlinear hydrodynamic equations that express the conservation of mass, momentum and energy for a fluid continuum. Although these equations can be linearized and readily solved for a system near thermodynamic equilibrium, the solutions of the nonlinear equations—required to describe fluids far from equilibrium—are generally neither unique nor obtainable.
Three groups see diamagnetic anomaly in copper chloride
Authors: Lubkin Gloria B.
Published: April 2009

A group of experimenters in Moscow has reported seeing very large diamagnetic signals from samples of copper chloride subjected to pressures of kilobars. The effect occurs at transition temperatures as high as 150 K. Two groups in the United States have seen related effects.
The idea of the neutrino
Authors: Brown Laurie M.
Published: April 2009

During the 1920's physicists came to accept the view that matter is built of only two kinds of elementary particles, electrons and protons, which they often called “negative and positive electrons.” A neutral atom of mass number A and atomic number Z was supposed to contain A protons, all in the nucleus, and A negative electrons, A–Z in the nucleus and the rest making up the external electron shells of the atom. Their belief that both protons and negative electrons were to be found in the nucleus arose from the observations that protons could be knocked out of light elements by alpha-particle bombardment, while electrons emerged spontaneously (mostly from very heavy nuclei) in radioactive beta decay. Any other elementary constituent of the atom would have been considered superfluous, and to imagine that another might exist was abhorrent to the prevailing natural philosophy.
The Multiple-Mirror Telescope
Authors: Carleton Nathaniel P. , Hoffmann William F.
Published: April 2009

In the fall of the year 1609 Galileo Galilei made the first systematic celestial observations that employed a telescope, thus helping to bring the skies from the realm of mythology into that of physics. Since his time, telescopes have increased nearly a hundredfold in size, with each major step providing a widening of our horizons. Galileo himself, however, went to some length to demonstrate how an increase in scale, without a change in design or in materials, must inevitably bring a structure to a size where it will no longer function properly, and eventually, to the point where it will even collapse under its own weight.
NMR and x-ray studies show large movements within proteins
Authors: Lubkin Gloria B.
Published: April 2009

X-ray crystallography provides information on the average structure of protein molecules. The images of atoms have always been broadened, but until the last few years this broadening was generally attributed to inaccuracies in the structure determination, lattice disorder and purely thermal vibration. Most crystallographers were skeptical about interpreting the temperature factors as structural motion. A typical small globular protein has a molecular weight of 20 000 a.m.u. and a diameter of 30–40 Å.
…and Cormack, Hounsfield for medicine
Authors: Schwarzschild Bertram M.
Published: April 2009

In the first year of this century Wilhelm Roentgen won the very first Nobel Prize in physics, for the discovery of a phenomenon which, in a remarkably short time, revolutionized medical diagnosis. On 11 October the Karolinska Institute announced that this year's Nobel Prize for Physiology and Medicine has been awarded jointly to a physicist and an engineer, for their contributions to what is widely regarded as the most revolutionary development in radiography since Roentgen's discovery of x rays. Allan Cormack, professor of physics at Tufts University (Medford, Mass.) and Godfrey Hounsfield, head of the medical-research division at EMI Ltd. (Middlesex, England) were awarded the Prize for their separate contributions to the development of computer-assisted tomography (see PHYSICS TODAY, December 1977, page 32).
New uses for amorphous silicon
Authors: Schwarzschild Bertram M.
Published: April 2009

Ever since 1975, when Walter Spear and Peter Le Comber of the University of Dundee in Scotland demonstrated that one could vary the conductivity of amorphous silicon over ten orders of magnitude by doping, there has been much excitement over the possibility of using this inexpensive material to make practical large-area solar cells. At about the same time, David Carlson and Christopher Wronski were producing amorphous-silicon solar cells with 5.5% efficiency at RCA.
Towards the absolute zero
Authors: Lounasmaa Olli V.
Published: April 2009

Low-temperature physicists are constantly trying to extend the temperature range accessible to experimental investigations closer and closer to the absolute zero. While the third law of thermodynamics prevents their ever reaching 0 K, they have long since surpassed Nature herself. The temperature of the cosmic background radiation is 3 K; below 3 K, we are creating new physics, hitherto unknown to the universe. And this has been done without any large expenditures of manpower or equipment—the most sophisticated weapons at the cold frontier of physics are inexpensive indeed.
Pulsed spallation neutron sources
Authors: Carpenter John M. , Blewitt Thomas H. , Price David L. , Werner Samuel A.
Published: April 2009

The discovery of the neutron in 1932, which indirectly led to the potentially catastrophic development of nuclear weapons on the one hand and to the beneficial development of nuclear-generated electricity on the other, has had another, less well-known, but scientifically important consequence: the provision of a uniquely sensitive and pervasive tool for probing condensed matter. Because they are neutral and because they interact mainly with nuclei, neutrons can penetrate into bulk material and provide information that is difficult to obtain with x rays or charged particles. Until recently, nuclear reactors provided the highest-intensity neutron sources. But lately another kind of source is promising to overcome the limitations of reactors. In these sources high-energy protons are made to collide with heavy nuclei, splitting off a large number of neutrons. The process is rather like making chips fly by hitting a rock with a hammer—what the geologists call “spallation.” These neutron spallation sources together with equipment such as that shown in figure 1 have already begun to provide us with useful information accessible in no other way.
Computer films for research
Authors: Scott John T.
Published: April 2009

Let's say you have just completed a computer simulation or numerical modeling of a complex system in your physical or chemical research. The data are likely to be delivered back to you in the form of mountains of Z-fold computer printout or stacks of Calcomp plots. Rather than picking your way through all this paper, why not turn the material into a short movie that can be projected over and over again, fast or slow, to show you whatever trends, discontinuities and so on your model possesses?
Phonon wind drives electron-hole droplets
Authors: Foerster Thomas von
Published: April 2009

If a semiconductor at low temperature receives a pulse of photons whose energy is larger than the band gap, the electrons and holes produced by the pulse are sometimes bound in neutral pairs, or “excitons.” A few years ago several groups of investigators found that in some materials at sufficiently low temperatures, excitons, which normally behave like atoms in a gas, condense to form drops of liquid (see PHYSICS TODAY, December 1973, page 17). Recent work has clarified the nature of these drops and has illuminated the interaction between the drops, phonons and other features of the crystal lattice. Much of this work was discussed at the Edinburgh Semiconductor Conference in September.
Radioisotope dating with accelerators
Authors: Muller Richard A.
Published: April 2009

A new method of detecting radioactive isotopes promises to have a revolutionary impact on the field of radioisotope dating. The technique, which was developed over the past two and a half years, consists of counting individual atoms of radioactive isotopes that have been ionized, accelerated to high energies, and then selected and identified. By detecting all—or a substantial fraction—of the atoms in the beam, this method has much greater sensitivity than the standard method, which detects only the tiny fraction of the atoms that decay during the counting period. The new “direct detection” method therefore will allow one to use much smaller samples and to measure much greater ages than the older “decay detection” method.