bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel applications of computers
Authors: Levi Barbara G.
Published: December 2008

BECAUSE most physicists now have access to a computer, they are able to tackle problems that might formerly have been unsolvable; at the very least they are able to solve their problems far more quickly and accurately. In a recent sample poll of its readers, PHYSICS TODAY learned that about 90% now use computers in their work. Most of these (85%) perform their calculations at the university or company computer center. Some 34% have computing facilities available to them on a time-sharing basis, and about 7% have their own computer. In approaching their problems, how many of these physicists are devising novel techniques?
Does the Microwave Background Have a Hump in its Spectrum?
Authors: Lubkin Gloria B.
Published: December 2008

The three-degree blackbody radiation may have a hump in its spectrum at about 1 mm, just where it peaks. Whether or not it's there, and if so, how it got there, is an intriguing mystery.
CERN Proposes Missing Magnets And 150 GeV for New Machine
Authors: Lubkin Gloria B.
Published: December 2008

The CERN 300-GeV project, plagued with foot-dragging, international intrigue, and tight money, and most recently confronted with Robert Wilson's announcement that the Batavia accelerator might yield a 500-GeV beam by 1 July 1971, has announced a new design approach that might salvage the project. In mid-April the new proposal was presented for discussion to European governments and European scientists; a decision is hoped for by October.
Spin-Flip Raman Laser Is Tunable Infrared Source
Authors: Lubkin Gloria B.
Published: December 2008

An intense laser source has been built which, by varying the applied magnetic field, is smoothly and continuously tunable in the infrared range of 10.9–13.0 microns. Other kinds of tunable sources—parametric oscillators—are available in the visible and near-infrared (but not infrared). At the APS Washington meeting late in April, Kumar Patel (Bell Labs) described the experiment. He and Earl Shaw shone a 10-micron CO2 laser onto an n-type indium antimonide crystal and applied a strong magnetic field (varied from 20 to 100 kG) perpendicular to the laser beam.
Three steps in the structure of matter
Authors: Weisskopf Victor F.
Published: December 2008

ORDER WAS BROUGHT to the chaos of the elements 100 years ago when Dimitri Ivanovich Mendeleyev arranged them in the periodic table. The riddle presented by the regularities in this table remained unsolved for 52 years, until Niels Bohr published his famous “Aufbauprinzip,” based on the quantum theory of the atom. Physical experimentation penetrated deeper into the structure of matter and revealed the properties of atomic nuclei. Similar periodicities were found when these nuclei were arranged according to the number of protons and neutrons. These regularities found their explanation in the shell model of the nucleus that was introduced in 1951 by J. Hans D. Jensen, Marie Goeppert-Mayer, Otto Haxel and Hans E. Suess. In the last two decades the proton and the neutron themselves were exposed to high-energy beams and many new short-lived entities were discovered. Recently Murray Gell-Mann, Kazuhiko Nishijima and Yuval Ne'eman discerned some order in the seemingly chaotic list of new “particles,” but the explanation of this order is still outstanding.
Photo of Single Atoms by Electron Microscope
Authors: Lubkin Gloria B.
Published: December 2008

A University of Chicago group using a high-resolution (5-Å) scanning electron microscope believes it has obtained pictures of single atoms of uranium and thorium deposited on a thin carbon substrate. Albert Crewe, Joseph Wall and John Langmore reported (Science 168, 1338, 1970) that by detecting the ratio of elastic to inelastically scattered electrons from the high-Z atoms, they were able to visualize individual atoms. The pictures, displayed on an oscilloscope, show bright spots in the kinds of locations expected by the experimenters. Because of the limitation of the 5-Å resolving power, the Chicago group constructed various molecules containing heavy atoms spaced further apart than 5 Å.
DESY Ring to Store 3.5-GeV Electrons, Positrons in 1973
Authors: Lubkin Gloria B.
Published: December 2008

The 3.5-GeV electron-positron storage ring being built at DESY (Deutsches Elektronen Synchrotron) in Hamburg should be finished at the end of 1973, according to Klaus Steffen, who spoke at a storage-ring conference in Princeton on 26 May.
US–Soviet collaboration to measure pion charge radius
Authors: Lubkin Gloria B.
Published: December 2008

This month four UCLA physicists hope to arrive at the High-Energy Physics Institute in Serpukhov to participate in the first joint experiment between Soviet and US physicists there. Darrell Drickey will head the US group and Edouard N. Tsyganov heads a group from Dubna. The collaboration will attempt to measure the charge radius of the pion by bombarding electrons with negative pions.
The future of physics
Authors: Dyson Freeman J.
Published: December 2008

What sort of physics should we be doing between now and the end of the century? This is a question I thought about recently when we at Princeton dedicated a new physics building; what would the people now in the building have a chance to do during their working lives?
International opportunities for physicists
Authors: Rothenberg Marian S.
Published: December 2008

“One of the best ways for the US to promote good relations with other countries is to export its science and technology, but, up until very lately, our scientists have been strongly domesticated.” William H. Taft III, special assistant in the State Department's Bureau of International Scientific and Technological Affairs, offered this opinion and suggested that if we could somehow link younger scientists with, tor example, the Peace Corps and the spirit of adventure, it would be to our advantage
Physics and social change
Authors: Brown George E.
Published: December 2008

We are a society in transition. Nearly all of our values and institutions appear to be shifting around us. Can physics help us understand the transition? The answer for me is clearly—yes. There is something unique in the history and philosophy of science, particularly physics, among all aspects of human culture. Physics welcomes change and knows how to use it. Certainly the experience of physics should help us to understand the nature of the transition we now face and to direct it for Man's benefit.
Cosmic-ray muon flux and the W particle
Authors: Lubkin Gloria B.
Published: December 2008

Four years ago Jack Keuffel and his collaborators at the University of Utah found an anomalous muon flux in cosmic rays. Their recent results are consistent with the observation of a W particle, or intermediate vector boson, whose mass is estimated at 20 to 40 GeV. The W particle is believed to be the carrier of the weak force, with a role comparable to that of the pion in nuclear forces. The Utah analysis depends on a model of the W put forth by James D. Bjorken (SLAC), Sandip Pakvasa, San-Fu Tuan and Walter Simmons (University of Hawaii). Results were reported late in August at the International Conference on Cosmic Rays in Hobart, Tasmania and the APS Division of Particles and Fields meeting in Rochester.
Ionizing-radiation standards for population exposure
Authors: Lieberman Joseph A.
Published: December 2008

Nuclear power generation currently represents the best hope for meeting America's long-term energy demands. The President, in his June 1971 message to the Congress on energy policy, emphasized the role that nuclear power must play in the future and called for additional funds for the AEC fastbreeder program, the most likely design to fulfill the need.
Teaching and the Environmental Challenge
Authors: Socolow Robert H.
Published: December 2008

Underlying the increased concern for environmental quality is the realization that the earth is vulnerable. This is a quantitative concept: the disturbances that Man is capable of generating on the earth are capable of substantially altering its character. Until recently Man's activity could not affect the viability of the earth in a substantial way in a period as short as a generation. Man's understanding of the earth's processes was also insufficient to detect and interpret the slower effects that he was responsible for. As Man's capacity to harm the earth increases, his capacity to monitor and control also increases—fortunately. The task ahead is to refine our understanding of the interaction of Man with his environment, to disseminate a consciousness of this interaction, and to make adjustments in values and behavior where necessary.
Continuous dye laser yields tunable output
Authors: Lubkin Gloria B.
Published: December 2008

If you want to make an organic dye laser operate continuously, just mix the dye with a little soapy water. That recipe worked for Otis G. Peterson, Sam A. Tuccio and Benjamin B. Snavely of the Eastman Kodak Research Laboratories. Since the group reported making a cw laser (Appl. Phys. Lett. 17, 245, 1970) it has managed to make it tunable in the range 5500–6500 Å and hopes soon to extend the work to other parts of the visible spectrum. Snavely says the dye laser should be tunable over the entire visible region. Although cw semiconductor lasers are tunable in the infrared, Snavely noted that the Kodak laser is the first cw tunable source in the visible range.
ASTRA project monitors atmospheric pollution
Authors: Lubkin Gloria B.
Published: December 2008

Astronomy, a field for which few have claimed relevance, is now becoming relevant to a pressing problem, atmospheric pollution. It turns out that those pesky atmospheric contaminants that have been annoying astronomers looking at the sun and other stars, have been leaving tell-tale lines on spectra, which can be measured to infer their presence and strength. Serendipitously, for decades observatories throughout the world have been collecting plates from which such pollution data can be inferred, which can now be used to establish trends, either regionally or globally.
Hydrogen laser holds record for short wavelength
Authors: Lubkin Gloria B.
Published: December 2008

Rodney Hodgson of IBM Research has built the shortest-wavelength laser ever made, making hydrogen lase in the vacuum ultraviolet on eighteen lines between 1520 and 1615 Å, corresponding to photon energies of about 8 eV. Previously the shortest wavelength was 2120 Å, obtained by frequency multiplication of 10 600-Å light from a neodymium-doped glass laser. The new vacuum uv laser is expected to be useful in the study of chemical reactions and the interaction of high-energy photons with matter.
Introducing the black hole
Authors: Ruffini Remo , Wheeler John A.
Published: December 2008

The quasistellar object, the pulsar, the neutron star have all come onto the scene of physics within the space of a few years. Is the next entrant destined to be the black hole? If so, it is difficult to think of any development that could be of greater significance. A black hole, whether of “ordinary size” (approximately one solar mass, 1 M⊙), or much larger (around 106 M⊙ to 1010 M⊙, as proposed in the nuclei of some galaxies) provides our “laboratory model” for the gravitational collapse, predicted by Einstein's theory, of the universe itself.
Plasma Physics Applied to Cosmology
Authors: Alfvén Hannes
Published: December 2008

The study of astrophysics in modern times should essentially involve the application of laboratory results to cosmical problems, with help from theoretical physics. In the realm of plasma physics, there appears to be no reason why known basic laws, formulated in the laboratory, should not hold just as well at the astrophysical and cosmological scale.
Is the Gum nebula the ghost of an exploding supernova?
Authors: Lubkin Gloria B.
Published: December 2008

A faint nebula that is one of the largest objects in our own galaxy and extends over 60 deg of the southern sky has been interpreted as the first clear example of a new class of galactic object, produced by the flash of ultraviolet and x-ray emission from an exploding supernova.
Muon-pair experiment: no new particles
Authors: Lubkin Gloria B.
Published: December 2008

The Brookhaven AGS, a proton synchrotron, has turned into a useful tool for studying electromagnetic interactions at high energy and momentum transfer. James Christenson, George Hicks, Leon Lederman, Peter Limon, Bernard Pope (Columbia) and Emilio Zavattini (CERN) have studied the massive muon pairs produced when high-energy protons strike uranium nuclei (Phys. Rev. Lett. 25, 1523, 1970). The experiment sets lower limits on the mass of the heavy photon proposed by T.D. Lee and Gian-Carlo Wick (Columbia) and on the intermediate vector boson. And the experiment offers a new way of elucidating the scaling and pointlike behavior in the nucleon.
One-dimensional antiferromagnets
Authors: Lubkin Gloria B.
Published: December 2008

Solid-state physicists have been talking about one-dimensional systems for many years. Recently neutron-scattering experiments have been performed on two different materials, which exhibit one-dimensional behavior. Tetramethyl ammonium manganese chloride, (CD3)4 NMnCl3, appears to act like a nearly ideal one-dimensional antiferromagnet, down to at least 1.8 K, according to M. T. Hutchings and Gen Shirane (Brookhaven), Robert J. Birgeneau (Bell Labs) and S. L. Holt (University of Wyoming). Shirane, John Skalyo Jr (Brookhaven). S. A. Friedberg and H. Kobayashi (Carnegie–Mellon University) had earlier found another substance, cesium manganese chloride dihydrate, CsMnCl3⋅2H2O, that also had some one-dimensional character, although not quite as striking.
Is the A2 meson split? Two experiments say no
Authors: Davis Harold L.
Published: December 2008

Two recent experiments have brought new life to the argument about whether the A2 meson is split—that is, whether it exists as two particles having identical properties except for a 3% difference in mass. The experiments, one performed at CERN by a CERN–Munich group and the other at Brookhaven, both report data indicating the A2 is not split. S. J. Lindenbaum, the leader of the Brookhaven group, presented data at the annual APS meeting in New York that he claims have less than one chance in a million of being consistent with a two-peak (dipole) mass formula. (The group has also published a letter in Physical Review Letters 26, 413, 1971.)
Photofragment spectroscopy looks at excited states
Authors: Rothenberg Marian S.
Published: December 2008

An elegant way to study dissociative molecular excited states has grown up during the past few years. At the “New Vistas for Chemical Physics” session at the New York American Physical Society Meeting, Kent R. Wilson of the University of California, La Jolla, described “photofragment spectroscopy,” which enables Wilson and his coworkers to study both the excited states of a molecule and the photodissociation fragments it produces, by measuring the mass, translational energy and angular distributions of the fragments. Detailed information on bound excited states has long been available from ultraviolet and visible spectroscopy, but such information for dissociative states has been rare, although the dissociative states are the more common. Because some of the molecules Wilson has studied are among the major photochemically active pollutants of the atmosphere, the results may be interesting to environmentalists as well as to chemical physicists.
Women in physics
Authors: Lubkin Gloria B.
Published: December 2008

Women physicists are a rare breed, but most of us agree that we need more of them. They have many problems in common with other professional women, but some are peculiar to physics. Many would like to work part time while raising families. Some feel that the system should have a bias built in to help women get into science and stay there. Others caution against lowering our standards. How do we provide models for young girls to identify with? Is the situation different abroad? Can the federal government help? Can genuine discrimination be observed?
Theory of amorphous semiconductors
Authors: Cohen Morrel H.
Published: December 2008

“Potential” is the word that first comes to my mind in thinking about the field of amorphous semiconductors. The field is potentially very large because of the wide range of phenomena and materials it encompasses. The phenomena lend themselves to a multitude of potential technological applications (see box). What I am concerned with here, however, is the challenge offered by amorphous semiconductors to our theoretical understanding.
Finding a better value for G
Authors: Beams Jesse W.
Published: December 2008

The gravitational proportionality constant G, although one of the first constants measured and perhaps the most fundamental and universal constant in Nature, is now the least accurately known. G, which relates the force F between two particles to their masses m1 and m2 and the distance d between them F = −Gm1m2/d2 is now known only with an accuracy of about one half of one percent. Because many contemporary techniques, such as in geophysics, require a good knowledge of G, as well as for purely theoretical interests, a group of us at the University of Virginia, Charlottesville, have been developing the apparatus shown in figure 1 to measure the absolute value of G as well as its possible variation with time or other factors.
Optical modulation of electron beam
Authors: Lubkin Gloria B.
Published: December 2008

Recently many physicists have become intrigued with trying either to explain or to duplicate the Schwarz–Hora effect, in which an electron wave is apparently modulated by a light wave. In an invited paper at the March APS meeting Helmut Schwarz (Rensselaer Polytechnic Institute, Hartford Graduate Center) discussed his most recent observations of the effect, first reported by himself and Heinrich Hora (Max Planck Institute, Garching, Germany) in June 1968 (Bull. Amer. Phys. Soc. 13, 897, 1968 and Appl. Phys. Lett. 15, 349, 1969).
Laser earth-strain gauge to search for gravity waves
Authors: Rothenberg Marian S.
Published: December 2008

An extremely stable laser developed at the Joint Institute for Laboratory Astrophysics, Boulder, Colorado, is providing a sensitive way to measure earth strain. Judah Levine and John L. Hall have built an interferometric strain gauge whose key element is a methane-stabilized 3.39-micron helium–neon laser at the Poorman's Relief Mine near Boulder. The stabilized He–Ne laser is beat against a second He–Ne laser locked to a 30-meter Fabry–Perot interferometer and fluctuations in the beat frequency are a direct measure of changes in the 30-meter path length.
On physics and employment of physicists in 1970
Authors: Koch H. William
Published: December 2008

The American Institute of Physics has ended its fourth decade in a year of economic turmoil for science—one accompanied by an abruptly dismal job market for physics PhD's and by concern about unemployment and underemployment of physicists generally. Let us here review the contributions, education and employment of physicists during AIP's 40 years, so as to place the 1970 experiences in perspective and so understand them better. This perspective will allow us to look at the future of physics and physicists with the insight we need if we are to avoid a repetition of the current difficulties.
Four decades of AIP
Authors: Barton Henry A.
Published: December 2008

The American Institute of Physics began in October 1931, a time of great difficulty for our science. This was the decade of the Great Depression, and a widespread “stop-science” movement blamed us for society's problems. It was also a time of divisiveness within physics: In 1899 one group, the American Physical Society, could encompass all physicists, but separatism had given rise to five societies. The leaders of that time, men such as Paul D. Foote, George B. Pegram, F. K. Richtmyer and Karl T. Compton, conceived of the rather close federation that is AIP to bring physicists together again, to improve the relations between physics and the rest of society and, not incidentally, to serve as the publisher of the increasingly important US physics literature.
Saclay and Argonne see nuclear quartet states
Authors: Lubkin Gloria B.
Published: December 2008

If you bombard Fe56 with O16 ions, you can observe C12 ions being emitted, which means that an alpha particle (really two protons and two neutrons whose relative motions are probably correlated as they are in an alpha particle) has been incorporated in the residual nucleus—in this case Ni60. The spectrum shows certain selected states and not others. That is, at certain specific energies the alpha particles find an easy way to get in—the system appears to resonate. Such experiments with alpha-particle transfer reactions are exciting great interest among nuclear physicists.
Ultrafast laser pulses
Authors: DeMaria Anthony J. , Glenn William H. , Mack Michael E.
Published: December 2008

By “ultrafast” we mean those light pulses that last from about 10−13 seconds to a few tens of picoseconds. The anticipation of using them to study ultrafast processes in physics and chemistry has stimulated efforts to produce these pulses, and the results have been good; in 1962 the shortest pulse available was 10−8 sec, but by 1968, 10−13-sec pulses had been produced at powers up to 10−12 watts. Progress has been due largely to the perfection of “mode-locking” methods, through which we arrange the phase relations between the axial modes of the laser. Here we shall discuss the ways ultrafast pulses are produced and measured. Then we can consider their usefulness in, for example, studying stimulated scattering, measuring excited-state lifetimes and creating high-temperature plasmas.
A mathematician's version of the fine-structure constant
Authors: Lubkin Gloria B.
Published: December 2008

A theoretical paper that predicts a value for the fine-structure constant α = e2/ℏc in terms only of simple rational powers of integers and π, agrees with the experimental value for α within one-half part per million, that is within one-third standard deviation or less. The present experimental accuracy of α (about 1.5 ppm) corresponds roughly to the thickness of a sheet of paper out of the length of a football field.
Livermore's new linear accelerator
Authors: Lubkin Gloria B.
Published: December 2008

A linac that can accelerate either positrons or electrons is now operating at Lawrence Radiation Laboratory, Livermore. The accelerator can produce variable-energy beams of up to 100-MeV electrons or 80-MeV positrons. The positrons are used to produce a high-intensity monochromatic photon beam that will explore photonuclear processes over a wide energy range. The electrons will primarily be used for neutron-physics studies through creation of a pulsed neutron source.
Quantum nature of superfluid helium
Authors: Putterman Seth J. , Rudnick Isadore
Published: December 2008

Low-temperature physics owes its existence to liquid helium, the refrigerant that permits investigation of phenomena occurring at a few degrees Kelvin. But liquid helium is fascinating in its own right, and the goal of understanding its “superfluidity” below 2.17 K has stimulated both experimenters and theorists.
Superconducting magnets
Authors: Hulm John K. , Kasun Don J. , Mullan Edward
Published: December 2008

In the last ten years we have seen the development of high-field superconducting magnet technology from the announcement, in 1961, of the first solenoids to the present day, when around a thousand magnet systems are in use in scientific laboratories throughout the world. A scientist interested in magnetic-field effects can now obtain a reliable magnet to generate a homogeneous and steady field in the 50–100 kilogauss range for a capital investment of about 25 cents per gauss.
Chain of pellets transfers charge in electrostatic accelerator
Authors: Lubkin Gloria B.
Published: December 2008

A new way of transferring charge in an electrostatic accelerator has been developed by the National Electrostatics Corp in Middleton, Wisconsin. Instead of using the traditional Van de Graaff belt-charging system, the “Pelletron” system consists of an endless chain of metal pellets joined by solid links of insulating material such as molded nylon; the pellets carry charge to the high-voltage terminal. Other charge-transfer devices used in electrostatic machines of the past include the rotating glass disc of the Wimshurst machine and the rotating plastic cylinder of the SAMES machines. Pelletron machines offer improved dependability and voltage stability over belt-charged electrostatic machines, according to Raymond G. Herb, president of the corporation.
Eskimo roller
Authors: Scott John T.
Published: December 2008

Eskimo roller. Actually James C. Sindelar is not an eskimo but an associate professor of electrical engineering at New Hampshire Technical Institute. He wrote the winning entry in the competition, sponsored by the Old Town Canoe Company, advertised in the January issue of physics today; our photograph shows him in the slalom kayak that was awarded as the competition prize.
How accurately can temperature be measured?
Authors: Gray William T. , Finch Donald I.
Published: December 2008

Suppose you have been asked to measure the temperature of an object known to be at around 1000°C. Being a knowledgeable physicist, you know that the most accurate procedure is to obtain the best thermocouple you can and use it carefully, in accordance with the manufacturer's instructions. The calibration table that comes with the instrument charts emf values to the nearest microvolt, corresponding to about 0.1°C, and with practice you find you can get reproducible readings within this interval. Does this mean that you are measuring temperature to ±0.1°C accuracy?
The Gum Nebula—A new kind of astronomical object
Authors: Maran Stephen P. , Brandt John C. , Stecher Theodore P.
Published: December 2008

The Gum Nebula is seen on photographs of the southern skies as an extensive region of ionized hydrogen that surrounds the well known Vela X supernova remnant. One of the largest objects in our galaxy, the Nebula was first recognized as a single emission complex by Colin S. Gum during the 1950's. Until recently, astronomers assumed that it was a “Strömgren sphere,” excited by ultraviolet light from the hot stars gamma Velorum and zeta Puppis within it. This excitation process accounts for the Orion Nebula and other H-II regions. The synchrotron and thermal bremsstrahlung mechanisms account for the radiation from supernova remnants, such as the Crab Nebula and Vela X; these objects consist of rapidly expanding matter ejected by the supernova explosions.
Poloidal divertor experiment
Authors: Bennett Floyd C.
Published: December 2008

Construction has begun on the Poloidal Divertor Experiment at Princeton University's Plasma Physics Laboratory. The $18-million device, expected to begin operation by December 1977, will be used to test the effectiveness of poloidal field divertors and magnetic limiters to control impurities in tokamaks.
Civil defense in limited war—a debate
Authors: Broyles Arthur A. , Wigner Eugene P. , Drell Sidney D.
Published: December 2008

Civil defense, once a hotly debated issue of the 1960's, has again surfaced as a topic of controversy. It reappears amid the discussions of possible new strategies being proposed by the Defense Department. In January 1974, the then Secretary of Defense James R. Schlesinger announced the intention of the US to develop long-range ballistic missiles of unprecedented accuracy. Because such weapons would have a relatively small error radius their yield would not have to be as large to be effective against military targets such as land-based offensive missiles. Hence the Defense Department has raised the possibility of a limited nuclear war with counterforce strikes (that is, against the opponent's offensive force) coupled with a program of civil defense to ensure a minimal level of civilian casualties.
Corrections
Authors: Anderson P. W.
Published: December 2008

Some points that appeared in the published version of my article on Brian Josephson (November, page 23) require clarification:

The article states that I served as nominal head of the Solid State Theory Group at the Mond Laboratory in 1961–2. I could not have done this as a visiting lecturer, and the Mond Laboratory is a subdivision of the Cavendish Laboratory specializing in low-temperature experimental physics and has never had a formal theoretical group. The group of which I am now head is a division of the Cavendish Laboratory of which Brian Josephson is now a member.

I am employed both by Bell Telephone Laboratories and by Cambridge University.

I travelled to Kyoto to attend and speak at the meeting and was therefore asked by Josephson and the committee on the London prize to accept it for him, since he was unable to, and to give an appreciation of his work, which was the source of the PHYSICS TODAY article.
Calculation of first and second static hyperpolarizabilities of one- to three-dimensional periodic compounds. Implementation in the CRYSTAL code.
Authors: Ferrero Mauro , Rérat Michel , Kirtman Bernard , Dovesi Roberto
Published: December 2008

A computational scheme for the evaluation of the static first (β) and second (γ) hyperpolarizability tensors of systems periodic in 1D (polymers), 2D (slabs), 3D (crystals), and, as a limiting case, 0D (molecules) has been implemented, within the coupled perturbed Hartree–Fock framework (CPHF), in the CRYSTAL code, which uses a Gaussian type basis set. This generalizes to 2D and 3D the work by Bishop et al. (J. Chem. Phys. 114, 7633 (2001)). CPHF is applied for β and γ (the polarizability tensor α is also reported for completeness) of LiF in different aggregation states: finite and infinite chains, slabs, and cubic crystal. Correctness of the computational scheme and its numerical efficiency are documented by the trend of β and γ for increasing dimensionality: for a finite linear chain containing N LiF units, the hyperpolarizability tends to the infinite chain value at large N, N parallel chains give the slab value when N is sufficiently large, and N superimposed slabs tend to the bulk value. High numerical accuracy can be achieved at relatively low cost, with a dependence on the computational parameters similar to that observed for field-free self-consistent field (SCF) calculations.
Deformation behavior of an amorphous Cu64.5Zr35.5 alloy: A combined computer simulation and experimental study
Authors: Mendelev M. I. , Ott R. T. , Heggen M. , Feuerebacher M. , Kramer M. J. , Sordelet D. J.
Published: December 2008

Molecular dynamics (MD) simulations were performed to examine the temperature-dependent elastic properties and high-temperature deformation behavior of a Cu64.5Zr35.5 amorphous alloy. From the simulations we find that the elastic constants of the amorphous solid and supercooled liquid exhibit an approximately linear temperature dependence. The predicted temperature dependence of the Young’s modulus for the amorphous solid obtained from the MD simulations is in good agreement with experimental measurements using dynamic mechanical analysis. Furthermore, the high-temperature plastic deformation behavior determined by MD simulations is qualitatively in good agreement with results from plastic deformation experiments performed on 1 mm diameter Cu64.5Zr35.5 metallic glass rods at 698 K. Notably, the MD simulations reveal that the flow softening regime of the stress-strain curve corresponds to an increase in the free volume in the atomic structure. Moreover, the simulations indicate that the atomic mobility significantly increases within the same regime.
Electron binding motifs in the (CS2)n− (n>4) cluster anions
Authors: Habteyes Terefe , Sanov Andrei
Published: December 2008

Photoelectron imaging spectroscopy of (CS2)n−, n>4, reveals a new state with an electron binding energy smaller than that of any of the corresponding CS2− and C2S4− states known to date. With support from ab initio calculations, two long-lived, metastable binding motifs with small electron binding energies are discussed for these clusters. The first is a solvent network permeating state, where the excess electron is delocalized over a number of linear CS2 molecules. The second is an excited B21 state of the core CS2− anion stabilized at a slightly bent geometry by the solvation interactions. Based on the observed solvation-induced shifts in binding energy, the second motif is favored.
Renner–Teller coupled-channel dynamics of the N(D2)+H2 reaction and the role of the NH2 Ã A21 electronic state
Authors: Gamallo Pablo , Defazio Paolo , González Miguel , Petrongolo Carlo
Published: December 2008

We present Renner–Teller (RT) and Born–Oppenheimer (BO) coupled-channel (CC) dynamics of the reaction N14(D2)+H12(X Σ1g+)→NH(X Σ3−)+H(S2), considering both NH2 coupled electronic states, X̃ B21 and Ã A21, and Coriolis interactions. We use the best available potential energy surfaces (PESs), and we obtain initial-state-resolved reaction probabilities, cross sections, and rate constants through the real wavepacket and flux methods, taking into account the nuclear-spin statistics for both electronic states. Contrasting RT-CC with more approximate results, we point out the role of RT and Coriolis couplings, and discuss the importance of the Ã A21 excited state on the initial-state-resolved dynamics and on the thermal kinetic rate. Confirming the previous results, RT couplings transfer partly the reactivity from X̃ B21 to Ã A21, and CC calculations are necessary to obtain accurate high-energy cross sections. When H2 is initially rotating, RT couplings enhance strongly the electronic-state-resolved Ã A21 reactivity. Considering the nuclear-spin statistics for both electronic states, we find out that the Ã A21 state plays a significant role in the rotationally resolved dynamics of N(D2)+ortho-H2. However, the BO–X̃ B21 approximation gives a thermal rate that is slightly smaller than the one obtained by the RT-CC calculations. This implies that this usual approximation is acceptable to calculate unresolved kinetic data of the title reaction. Our calculated rate constant values within the 213–300 K temperature interval are in excellent agreement with the experimental ones.
Influence of the illumination on weak antilocalization in an AlxGa1−xN∕GaN heterostructure with strong spin-orbit coupling
Authors: Zhou W. Z. , Lin T. , Shang L. Y. , Sun L. , Gao K. H. , Zhou Y. M. , Yu G. , Tang N. , Han K. , Shen B. , Guo S. L. , Gui Y. S. , Chu J. H.
Published: December 2008

The weak antilocalization effects of the two-dimensional electron gas in a high mobility AlxGa1−xN∕GaN heterostructure have been investigated by means of magnetotransport measurements before and after illumination. The zero-field spin splitting mainly arising from the Rashba spin-orbit coupling effect as a function of electron concentration as well as a function of temperature is studied using the weak antilocalization analysis. The Rashba spin-orbit coupling constant α deduced using the weak antilocalization analysis shows a rapid decrease with the increase of the measured electron concentration.
Kinetic theory for low-frequency turbulence in magnetized plasmas including discrete-particle effects
Authors: Yoon Peter H. , Fang Ta-Ming
Published: December 2008

In a recently developed kinetic theory for low-frequency turbulence propagating parallel to the ambient magnetic field [P. H. Yoon, Phys. Plasmas 14, 10230 (2007); P. H. Yoon and T.-M. Fang, Phys. Plasmas 14, 102303 (2007); P. H. Yoon and T.-M. Fang, Plasmas Phys. Control. Fusion 50, 085007 (2008)], the effects arising from the discrete particle nature, or the spontaneous thermal effects were ignored. Such an assumption thus limited the theory to purely collisionless “Vlasov” regime. In the present paper the previous formalism is generalized to include discrete-particle effects by reformulating the problem on the basis of the Klimontovich equation. The new terms that appear in the particle and wave kinetic equations as a result of the new formalism are the spontaneous drag term associated with the particles and the spontaneous emission and scattering terms associated with the waves.
Predictions of melting, crystallization, and local atomic arrangements of aluminum clusters using a reactive force field
Authors: Ojwang’ J. G. O. , van Santen Rutger , Kramer Gert Jan , van Duin Adri C. T. , Goddard William A.
Published: December 2008

A parametrized reactive force field model for aluminum ReaxFFAl has been developed based on density functional theory (DFT) data. A comparison has been made between DFT and ReaxFFAl outputs to ascertain whether ReaxFFAl is properly parametrized and to check if the output of the latter has correlation with DFT results. Further checks include comparing the equations of state of condensed phases of Al as calculated from DFT and ReaxFFAl. There is a good match between the two results, again showing that ReaxFFAl is correctly parametrized as per the DFT input. Simulated annealing has been performed on aluminum clusters Aln using ReaxFFAl to find the stable isomers of the clusters. A plot of stability function versus cluster size shows the existence of highly stable clusters (magic clusters). Quantum mechanically these magic clusters arise due to the complete filling of the orbital shells. However, since force fields do not care about electrons but work on the assumption of validity of Born–Oppenheimer approximation, the magic clusters are therefore correlated with high structural symmetry. There is a rapid decline in surface energy contribution due to the triangulated nature of the surface atoms leading to higher coordination number. The bulk binding energy is computed to be 76.8 kcal/mol. This gives confidence in the suitability of ReaxFF for studying and understanding the underlying dynamics in aluminum clusters. In the quantification of the growth of cluster it is seen that as the size of the clusters increase there is preference for the coexistence of fcc/hcp orders at the expense of simple icosahedral ordering, although there is some contribution from distorted icosahedral ordering. It is found that even for aluminum clusters with 512 atoms distorted icosahedral ordering exists. For clusters with N≥256 atoms fcc ordering dominates, which implies that at this point we are already on the threshold of bulklike bonding.
Photoluminescence dynamics of exciton-exciton scattering in a lightly alloyed InGaN thin film
Authors: Nakayama M. , Sakaguchi K.
Published: December 2008

We have investigated the photoluminescence (PL) dynamics of a lightly alloyed In0.02Ga0.98N thin film under intense excitation conditions at 10 K. In the In0.02Ga0.98N thin film, a PL band due to exciton-exciton scattering, the so-called P band, appears with a thresholdlike nature in the excitation-power region higher than ∼3 μJ/cm2. Under the condition that the exciton-exciton scattering occurs, the PL-decay profile consists of a fast decay component of the P band (of the order of 10 ps) and a slow decay component of a localized exciton band. The decay time of the P band gradually shortens with increasing excitation power. The change in the decay time can be explained qualitatively by the photon-like characteristics of the lower polariton branch that is the final state of the P emission. Furthermore, we have clearly observed the temporal change in the peak energy of the P band, which reflects an effective temperature of the excitonic system. The energy shift of the P band suggests that the P emission process reaches equilibrium with the lattice temperature after ∼100 ps.
A solid-liquid-vapor mechanism for anisotropic silicon etching
Authors: O’Toole Martin , Boland John J.
Published: December 2008

Here we report on a technique for anisotropic etching of silicon similar to the well established vapor-liquid-solid technique for the growth of semiconductor nanowires. By annealing a patterned gold line on a H terminated silicon surface, Si atoms diffuse into the Au to form a eutectic phase. Upon exposure to etchant gases the dissolved silicon reacts and desorbs from the eutectic phase causing additional silicon to diffuse from the substrate to re-establish the equilibrium eutectic composition. In this manner the patterned eutectic material becomes anisotropically etched into the silicon substrate, in a process we call solid liquid vapor etching.
Drift current dominated terahertz radiation from InN at low-density excitation
Authors: Lin K. I. , Tsai J. T. , Wang T. S. , Hwang J. S. , Chen M. C. , Chi G. C.
Published: December 2008

This letter investigates the polarity of terahertz radiation from indium nitride (InN) excited by femtosecond optical pulses wherein a central wavelength of around 790nm is measured. The InN epilayers are grown by metalorganic chemical vapor deposition on sapphire and silicon substrates. The polarity of the terahertz radiation field from InN is opposite to that from p-InAs whose radiation mechanism is dominated by the photo-Dember effect indicating that the dominant radiation mechanism in InN is the drift current induced by the internal electric field at low-density excitation below 590nJ∕cm2. The internal electric field consists of the surface accumulation field and the spontaneous polarization-induced electric field. In addition, since no azimuthal angle dependence of the terahertz radiation is observed, the optical rectification effect is ruled out. By comparing the wave forms of terahertz radiation from the front and the back of the InN sample grown on sapphire in reflection geometry, the N polarity of the InN sample is confirmed.
Photoinduced reduction and pattern preservation of giant surface potential on tris(8-hydroxyquinolinato) aluminum(III) thin films
Authors: Ozasa Kazunari , Nemoto Shigeyuki , Isoshima Takashi , Ito Eisuke , Maeda Mizuo , Hara Masahiko
Published: December 2008

The characteristics and mechanisms of photoinduced reduction in giant surface potential (gSP) on tris(8-hydroxyquinolinato) aluminum(III) (Alq3) thin films were investigated and discussed from the results of the reduction dependences on exposure time/intensity and the preservation of photopatterned gSP. The reduction dependences are explained well with numerical-model calculation of surface potential reduction due to the drift of photoexcited carriers assuming the Poole–Frenkel formula for electron mobility. The preservation of patterned gSPs suggests the existence of deep traps involved in the carrier-drift mechanism.
Substrate orientation dependence of ferromagnetism in (Ga,Mn)As
Authors: Wilson M. J. , Xiang G. , Sheu B. L. , Schiffer P. , Samarth N. , May S. J. , Bhattacharya A.
Published: December 2008

We describe a comprehensive study of the properties of both ordered and random alloy Ga1−xMnxAs grown on (001), (311), (201), and (110) GaAs substrates. Magnetization measurements show a systematic variation in the Curie temperature with epitaxial orientation in both types of samples, even for the same average Mn concentrations. Electrical characterization and thermal annealing of the random alloy Ga1−xMnxAs samples suggest that the density of As antisite defects depends on the growth surface, providing an extrinsic origin for the observed dependence of Curie temperature on substrate orientation.
Dubna cyclotrons paired to accelerate xenon
Authors: Lubkin Gloria B.
Published: December 2008

Xenon ions have been accelerated to 7 MeV/nucleon or a total energy of 925 MeV, an energy sufficient to surmount the Coulomb barrier in any known nucleus. The xenon ions, with Z of 54, are expected to be very effective in the attempt to make supertransuranic elements near the island of stability.
Laser plus iron target:broad-band x-ray source
Authors: Lubkin Gloria B.
Published: December 2008

By bombarding a thick iron target with a high-power laser, a broad-band source of x rays has been produced. The conversion efficiency of 1.06-micron laser light into x rays is at least 10%, probably 15–20% and possibly 30–40%, according to Philip Mallozzi (Battelle Memorial Institute, Columbus), who announced his results at the Esfahan (Iran) Symposium on Fundamental and Applied Laser Physics in September.
Lamb-shift measurements in high-Z atoms test QED
Authors: Rothenberg Marian S.
Published: December 2008

Atomic physicists have been awaiting reliable measurements of the Lamb shift in high-Z atoms as a sensitive test of quantum electrodynamics. Now a team from Bell Telephone Laboratories reports a value of 780.1±8.0 GHz for carbon, atomic number 6, that agrees with the most recent predictions of QED, 783.7±0.25 GHz.
What future for medium-energy physics?
Authors: Kolstad George A.
Published: December 2008

According to Harvey Brooks, there are four main reasons for the support of scientific research: cultural, economic, social and educational. Needless to say, opinions differ as to the proper measure of Federal responsibility for each of these purposes. Brooks, who is chairman of the US National Academy of Sciences Committee on Science and Public Policy, goes on to describe four models of the research system based on these reasons for support:

▸ Science as a quasiautonomous, self-structuring activity that ultimately benefits society but must be left to develop according to its own internal dynamics if the social benefits are to be realized most efficiently (model attributed to Michael Polanyi and Derek de Solla Price)

▸ Science as a social overhead on applied research and development, aimed at specific social objectives and missions (model attributed to Alvin Weinberg)

▸ Science as a social overhead investment, in which research and education—in the broadest sense of the development of institutional and individual capacity to the maximum potential—are inseparable objectives (unattributed)

▸ Science as a tertiary industry or consumption good, representing the nonmaterial, nonproduction aspect of the goals and activities of an increasingly affluent society (model attributed to Stephen Toulmin)
Physics looks at waste management
Authors: Rose David J. , Gibbons John H. , Fulkerson William
Published: December 2008

The question of what role physics plays in the garbage business invites the casual answer: “Not much.” But that would be wrong, and not from any trivial viewpoint, such as the mechanics of garbage grinders. Admittedly, physics does not play the key role, and certainly what is known colloquially as “high physics” may be quite unresponsive to the problem. Nevertheless, the ethos of physics and recognizable physical principles have become peculiarly useful as part of the intellectual armamentarium of waste management. Surely we are biased—two of us are former physicists and one is a former physical metallurgist. We will try to convince you that we are serious and have a valid point of view.
Physics looks at solar energy
Authors: Meinel Aden Baker , Meinel Marjorie Pettit
Published: December 2008

The idea of using the sun as a source of energy has had a long history, but so far it has been a history of bright hope and dismal failure. In the middle 1950's newspaper headlines were full of glowing predictions of what solar energy could do for mankind; the first International Conference on Applied Solar Energy had been held, and solar energy seemed ready to take its place, along with peaceful uses of atomic energy and with interplanetary exploration, on Vannevar Bush's “endless frontier of science.” And now in the 1970's nuclear power reactors and spaceflight are realities, yet solar energy, as recently as a year ago, was dismissed by a National Academy of Science–National Research Council committee as of no importance in our future—despite the admitted “energy crisis” looming ahead. Whatever happened to the grand predictions? Our search into the history of solar energy started with this question, because we were curious to know if 1970 technology might yield a different result.