Waves & Packets
Mar. 18, 2013

Cold hydrogen molecules found on hot stars
Physics World
Using the Hubble Space Telescope's high-resolution Cosmic Origins Spectrograph to obtain the ultraviolet spectra, researchers have detected hydrogen molecules on the surfaces of several white dwarf stars. Molecular hydrogen normally would not form at the surface temperatures of these stars (>104 K). But the extreme gravitational forces may be causing hydrogen molecules to form — despite the heat, which would otherwise prevent their formation. From the strength of the spectral lines, the astronomers estimate there is about one hydrogen molecule for every 100,000 hydrogen atoms. Prior to this find, the hottest star known to have molecular hydrogen was our own, where sunspots, which are cooler than the solar surface, harbor the molecule. The surprising discovery should help astronomers gain a better understanding of the extreme conditions on these white dwarfs. Moreover, the deuterium spectra from these objects will give additional clues on the evolution of extrasolar planets. The paper detailing this discovery is published in the Astrophysical Journal Letters. More

ALMA astronomers find ancient starbursts through gravitational lensing
Max Planck Institute for Radio Astronomy
By following up on previous observations, and by using the resolving power of the new ALMA telescope, a multi-national team of astronomers has measured the distances to 23 highly redshifted dusty starburst galaxies. These galaxies are amongst the earliest ones formed in the universe, and these new observations refined our knowledge of their ages to unprecedented levels. Radiation from the star forming activity is natively in the blue and ultraviolet regions of the EM spectrum. But absorption by H2, O2 and H2O gas, which astronomers call dust, leads to subsequent emissions in the IR region. Expansion of the universe then leads to that IR radiation being shifted to millimeter and submillimeter ranges, the region in which ALMA operates. As detailed in the Nature paper, gravitational lensing and the high resolving power of ALMA allowed the astronomers to identify at least one clear spectral line for each of the 23 galaxies. These observations indicate that the fraction of dusty starburst galaxies at high redshifts is greater than previously thought.More

Researchers create super responsive graphene earphones
A team of materials physicists has demonstrated the use of graphene as the mechanical diaphragm in audio earphones. The diaphragm was made from an ultra-thin 30nm x 7mm sheet of graphene, fitted between a top and bottom layer of electrodes made of silicon coated with a thin layer of silicon dioxide. The speaker/earphone is straightforward in design and operation and has excellent frequency response across the entire audio frequency range (20HZ–20kHz), with performance matching or surpassing commercially available audio earphones. The researchers are predicting that graphene might possibly be the material of choice in future speakers in laptops and smartphones not only for their excellent sound output but also because of their energy conductivity abilities. They also have demonstrated how it can be mass-produced easier with new vapor techniques that could create much larger diaphragms. More

Ultrabright X-ray pulses show chemical reaction in real time
Scientists at the Linac Coherent Light Source at SLAC have revealed surprising details of a short-lived early state of carbon monoxide oxidation on a ruthenium crystal surface. Oxidation with ruthenium catalysts is extensively used in cars and other industrial applications. With CO absorbed on the Ru (001) surface, the crystal was excited with a UV laser pulse to stimulate desorption. Trailing the UV pulse with ultra-fast X-ray pulses probes the electronic state of the CO molecule during the surface bond breaking. The experiments and subsequent quantum chemical calculations, both described in Science, revealed a molecular state that did not overcome the desorption barrier, but was bonded less strongly than the chemisorbed state.More

Carbon monoxide and water signatures in distant planet show clues to its formation
Lawrence Livermore National Laboratory
Using the OSIRIS instrument on the Keck II telescope a multi-national team of scientists has made the most detailed examination yet of the atmosphere of a Jupiter-size like planet beyond our solar system. The finding, reported in Science, provides astrophysicists with additional insight to discern between two leading theories of planet formation. When stars form they are surrounding by a disk of material in which planets form. In the core accretion model of planet formation, planets form gradually as solid cores slowly grow big enough to start absorbing gas from the disk. But in the gravitational instability model, planets form almost instantly as parts of the disk collapses on itself. The planetary atmosphere provides a clue as to whether a system formed according to one model or the other. In this current work, the water and carbon monoxide spectra from the planet HR 8799c indicate that core accretion is the more likely model for its formation. More

Physicists find 3 new classes and 13 new families of solutions to 3-body orbit problem
Science Now
Using computer modeling, two physicists from the Institute of Physics Belgrade have identified 13 new families of periodic orbits for three equal masses moving in a plane under the influence of Newtonian gravity with zero angular momentum. Physical orbits correspond to closed paths on the sphere that avoid points that correspond to two of the masses being in the same place, i.e., a collision. The researchers devised a topological method to classify orbits into four classes based on geometric and algebraic symmetries which indicate by number of times they wind clockwise and counterclockwise around collision points. In this new classification scheme the previous families of solutions to this problem, i.e., the Lagrange-Euler, the Broucke-Hénon, and figure-eight, all belong to one class, while the 13 new families of solutions are classified into three new classes. The paper detailing this work is appears in Physical Review Letters. Supplemental material is available on the researchers' website.More

Spin of photoelectron from topological insulator can be controlled polarization of light
Berkeley Lab News center
A team of physicists from UC Berkeley and LBL have unexpectedly discovered that when the topological insulator bismuth selenide is hit with a laser beam, the spin polarization of the photo-emitted electrons can be completely controlled in three dimensions, simply by tuning the polarization of the incident light. This had been counterintuitive because spin of surface electrons in topological insulators are locked to their momentum, perpendicular to the direction of travel. The implications of this result, in terms of fundamental understanding of electronic states and applications, are profound. In the first instance the simple picture of spin texture, i.e., the relation between spin and momentum of the surface electrons in topological insulators is apparently more complex than has been assumed. But for applications, the idea of optically controlled spin polarization presents intriguing possibilities for spintronics. This research is reported in Nature Physics.More

Astronomers observe planets orbiting another star like never before
Astrobiology Magazine
Researchers at Caltech and the American Museum of Natural History have developed a new capability that enables them to simultaneously image and take low resolution near IR spectra of exoplanets amidst the bright glare of their parent star. The system, dubbed Project 1640, uses combination of an extreme adaptive optics system, an advanced coronagraph and hyperspectral imager, and a unique wavefront sensor calibration unit, which allows for the detection of objects up to ten-million times fainter than a star within a field of view of four arc seconds. The researchers have used the instrument to obtain images and spectra of all four known planets orbiting the star HR 8799, and reported their results in the Astrophysical Journal. The four planets have significantly different spectra. Though the four planets have similar luminosity they exhibit significantly different spectra. Researchers were able to identify the presence of methane, ammonia, ethylene, and perhaps carbon dioxide or hydrogen cyanide in differing amounts amongst the four planets indicating an intriguing diversity in planetary evolution.More

New details found of water's atomic structure and dynamics under extreme conditions
European Synchrotron Radiation Facility
At pressures above 22 MPa and temperatures above 374°C, beyond the critical point, water turns into a very aggressive solvent, a fact that is crucial for the physical chemistry of Earth's mantle and crust. But how the structure and dynamics of water is affected by these extreme conditions has long been an open research problem. A team of scientists has studied this problem using X-ray Raman scattering and ab initio dynamics calculations. Both the experimental and computational results indicate that the structure of water continuously develops from an ordered, polymerized structure to a disordered, marginally polymerized structure at supercritical conditions. That is, though there was some distortion in the hydrogen bond network, the microscopic structure of water remains spatially homogeneous. The results are reported in the Proceedings of the National Academy of Sciences of the United States of America. More

Superheated water under graphene can corrode diamonds
R&D Magazine
Superheated water trapped between a layer of graphene and a diamond surface becomes corrosive enough to cut the diamond. Apparently at high temperature, the chemical bonding between graphene and diamond is robust enough that the water molecules stay trapped between the two. This work is reported in Nature Communications. Previous work had explored the structure, hydrogen bonding, dielectric, diffusion and spectroscopical properties of water in a graphene slab, but this is the first experimental demonstration of how corrosive the trapped water can be.More

NSBP members visit South Africa to strengthen ties
NSBP members Kartik Sheth and Eric Wilcots along with NRAO astronomer Scott Ransom are in South Africa to cement linkages for a NRAO's faculty bridge program. NRAO currently operates four premier radio astronomy observatories: ALMA, JVLA, GBT and the VLBA. The visit is intended to foster partnerships in multi-wavelength astronomy research. Wilcots is board member of Southern Africa Large Telescope, the largest optical telescope in the southern hemisphere. Ransom is an expert on pulsar timing, a key science project at HartRAO. The team will also meet with high energy astrophysicists at North-West University, University of Johannesburg, and University of Witswatersrand, as well as astronomers and cosmologists at various institutions in Cape Town, Mafikeng and Durban.

Separately Jim Gates is participating in South Africa's SciFest, giving talks in a number on science policy and supersymmetry at venues around the country. He also met with science minister Derek Hanekom, who will in turn visit the United States in June. NSBP and SAIP are working together to add a science dimension to the South Africa-United States Strategic Dialogue.More

Feynman' double-slit thought experiment precisely performed in the lab
Physics World
Physicists in the U.S. and Canada have created a double-slit experiment that follows the precise methodology of Feynman's electron beam through a double-slit thought experiment. Feynman conceived of this experiment as a way of illustrating wave-particle duality in quantum mechanics. As reported in the New Journal of Physics, the team created a double slit in a gold-coated silicon membrane, in which each slit is 62 nm wide and 4 μm long with a slit separation of 272 nm. To block one slit at a time, a tiny mask controlled by a piezoelectric actuator was slid back and forth across the double slits. The electron beam's intensity was set low so that only one electron at a time would ever pass through the slits. As expected, a diffraction pattern was only detected when both slits were open to the beam. While no new physics was revealed, this demonstration is particularly important from an outreach perspective because unlike the biprism experiments of the past, it actually uses a physical double slit and is therefore more accessible to the public.More

Your time line for graduate school applications
Your time line towards applying to graduate school should begin in earnest in the summer before you are to graduate (assuming you will be graduating after the spring semester and want to go to graduate school right away). In June-August start thinking about what areas of physics interests you, and where you want to be in 5-10 years. You should use your advanced coursework, electives and senior research project to further explore your interests in physics. If you start practicing now your should be able to take the General GRE early in the coming summer. The test is given year-round at computer-based test centers located around the world. The physics subject GRE is still a paper and pencil based test. It is offered in early October, mid-November, and early April. Unless you are really ahead of the game and are ready for the physics GRE next month, you need to key on the fall administrations as the scores for the April 2014 test will not be available in time for an application for the following fall's class. More

Admissions criteria and diversity in graduate school
American Physical Society
There are about 180 physics programs listed in the AIP Graduate Programs book. The General GRE is required by 96 percent; a quarter of these have an explicitly stated minimum Quantitative GRE score for admission, with the median stated cut-off being 700. As educators, we naturally expect exams to be meaningful. Most people believe this is the case for the GRE exams, and may thus prefer high scores. But analysis of the data often finds no significant correlation between long-term success and GRE scores. The implications for diversity of using 700 as a minimum acceptable score are that nearly three quarters of Hispanics would be rejected, and significantly more than this for American Indians, African Americans, and Puerto Ricans; similarly, women are filtered out at a higher rate than men. Mixing cut-off scores with these racial and gender disparities sets the foundation of a glass ceiling erected by the lopsided treatment of minorities and women before they even set foot in grad school. More

National Society of Black Physicists jobs board postings
Summer Internship
Schuler Postdoctoral Fellowship
Postdoctoral Fellowship - Stanford Molecular Imaging Scholars Program
Physics Academic Coordinator I/Lecturer
Summer Undergraduate Researcher
Postdoctoral Research Associate Positions
Full-time Lecturer in Experimental Physics More

New details found of water's atomic structure and dynamics under extreme conditions
European Synchrotron Radiation Facility
At pressures above 22 MPa and temperatures above 374°C, beyond the critical point, water turns into a very aggressive solvent, a fact that is crucial for the physical chemistry of Earth's mantle and crust.More

Reconstructing the orbit of the Chelyabinsk meteoroid
A pair of Colombian scientists has made the first attempt to reconstruct the trajectory of the meteoroid (Chelby) that exploded over Chelyabinsk, Russia last month. Their analysis of the meteor's orbit, posted on arXiv, relies on an eclectic mix of data from car dashboard and stationary security cameras.More

Long predicted atomic collapse state observed in graphene
Lawrence Berkeley Laboratory
The extraordinary properties of graphene have allowed physicists to experimentally observe atomic collapse, a long sought after holy grail of nuclear and atomic physics.More

Latest research from Journal of Physics: Condensed Matter
IOP Publishing
Control of the surface electronic structure of SrTiO 3 (001) by modulation of the density of oxygen vacancies

Anomalous bulk compression behaviour in a hyperstoichiometric uranium-dioxide–thorium-dioxide solid solution

Plasmon excitation in single-walled carbon nanotubes probed using charged particles: comparison of calculated and experimental spectra

Mechanical coupling in homogeneously deformed single-wall carbon nanotubes

Electronic and magnetic structure of the Cr(001) surface


Latest research from Progress in Materials Science
Effect of chemical doping of boron and nitrogen on the electronic, optical, and electrochemical properties of carbon nanotubes

Nanoporous anodic aluminium oxide: Advances in surface engineering and emerging applications

Engineering biocompatible implant surfaces Part I: Materials and surfaces

Engineering biocompatible implant surfaces: Part II: Cellular recognition of biomaterial surfaces: Lessons from cell–matrix interactions

Biomimetic optical materials: integration of nature's design for manipulation of light