Waves & Packets
Mar. 10, 2012

Antihydrogen undergoes its 1st measurement
Ars Technica
A report in Nature has shown the first "spectra" of trapped antihydrogen atoms, showing the energy required to change the spins of its positrons. The spin-flip transition involves placing antihydrogen in a microwave resonant cavity to manipulate the relative orientations of the antiproton and positron spins. From a theoretical point of view, if the spin-flip transition occurs even at a slightly different energy for antihydrogen than it does for hydrogen, it means a fundamental asymmetry in nature. While the experiment lacked the precision needed to distinguish any differences between matter and antimatter, it highlights how to proceed if we're going to make a successful measurement in the future.More

Daya Bay announces discovery of a new kind of neutrino transformation
The Daya Bay Reactor Neutrino Experiment, a multinational collaboration operating in the south of China, has reported the first results of its search for an elusive neutrino transformation mixing angle, which is a quantification of the transformation of one neutrino flavor to another. The copious data indicate that sin2 2θ13, is equal to 0.092 plus or minus 0.017. This particular mixing angle is measured with precision unmatched by other mixing angle measurements.More

Physicists measure the skin of a nucleus
Science Now
Atomic nuclei are covered with a nearly pure layer of neutrons—the "neutron skin." Now, for the first time, nuclear physicists have measured the thickness of that skin by firing electrons at a thin sheet of lead-208. Each lead-208 nucleus has 82 protons and 126 neutrons. The protons' electric field deflects the trajectories of the electrons. By studying that deflection, researchers can measure the distribution of protons to determine a nucleus's "proton radius." To measure the "neutron radius" of lead-208, the researchers had to fire spin polarized electrons at the nuclei. Subtracting neutron radius from the proton radius gives the neutron skin thickness. And such a result can refine nuclear models important for nucleosynthesis and for explaining features of neutron stars. More

Analysis of final Tevatron data shows hint of Higgs boson
Science Now
Physicists working at the Fermilab, having analyzed all the data collected at the Tevatron, report that they see hints of the Higgs. The CDF and D0 teams see excesses with roughly the same mass, at about 125 giga-electron volts as the ATLAS and CMS teams, albeit with poorer mass resolution. The last Tevatron data does not have the signal strength necessary to claim discovery. That distinction will more than likely be left to the LHC teams when they start taking data again later this fall. But the Tevatron teams will have more than a fantastic story of what could have been; and who knows what untold exciting physics exists in the reams and reams of data yet to be analyzed.More

Proposed cloaking device for water waves could protect ships at sea
Science Now
Yet another example of cloaking is being reported in Physical Review Letters; this time of mechanical fluid waves. Utilizing a nonlinear resonance concept that occurs between surface and internal waves and mediated by specific bottom topography, it should be possible to hide an object floating on the sea from passing waves. The technique depends upon density stratification in a column of ocean water. A wave that moves across the surface can be transformed into a wave at the interface between two layers, and eventually back again. This can be done by installing ripples on the sea floor that have just the right wavelength. The effect is that the surface remains undisturbed as the wave energy is displaced to the interface below the surface.More

Researchers capture 1st images of atoms moving in a molecule
Science Daily
To take pictures of the atomic movements in a molecule a team of researchers used ultrafast laser pulses to knock one of the molecule's electrons out of its natural orbit. As the electron relaxed back into the molecule, it scattered off the molecule, and the diffraction pattern gave a snapshot of atomic positions. The technique, called laser induced electron diffraction, is commonly used in surface science to study solid materials. This is the first time anyone has used LIED to study a single molecule as it formed. These initial experiments, reported in Nature, were done with simple and well-characterized diatom reactions, but LIED opens up the possibility of optically induced ultrafast diffraction studies of more complex chemical reactions, as well as a way to possibly control chemical reactions on an atomic level. More

Galactic pile-up leaves behind mysterious dark matter core
Using gravitational lensing to show its presence, astronomers have found an enormous and strange clump of dark matter left behind following a violent collision of galaxy clusters. The clump is located in the Abell 520 cluster, a diffuse collection of galaxies located 2.4 billion light-years away in the constellation Orion. A 2007 study of Abell 520 found typical amounts of dark matter with visibile matter, except one gigantic and perplexing "dark core" that should have attracted large amounts of visible matter yet contained almost no galaxies. Most astronomers dismissed this observation as a contamination or artifact in the data. But a follow-up analysis with the Hubble space telescope confirms the odd dark core exists, throwing researchers for a loop. The latest results are reported in the Astrophysical Journal.More

Physicists put a new twist on radio
Physics World
Physicists in Italy have shown that, like light, radio waves can have their wavefronts twisted so that they take on a corkscrew shape. The researchers have successfully transmitted twisted beams several hundred meters across the lagoon in Venice using a specially shaped antenna. They believe that such beams could dramatically enhance the information capacity of wireless communications by multiplying the number of channels that can be encoded in a given frequency range. This work, described in the New Journal of Physics, was inspired by research on black holes, and researchers hope to use the technique on the Very Large Array radio telescope (and possibly the planned Square Kilometer Array) to make measurements of the black hole at the center of the Milky Way to prove that it is indeed rotating. More

Physicists generate frequency comb with more than 100 terahertz bandwidth
In a Nature Photonics paper, a team of physicists detail their success in generating a frequency comb that divides a single color of light into a series of evenly spaced spectral lines that spans a more than 100 terahertz bandwidth by exciting a coherent collective of atomic motions in a semiconductor silicon crystal. The ability to modulate light with such a bandwidth could increase the amount of information carried by more than 1,000 times when compared to the volume carried with today's technologies. The team investigated the change in reflectivity after excitation with an intense laser pulse. Following the excitation, the team observed that the amount of reflected light oscillates at 15.6 THz, the highest mechanical frequency of atoms within a silicon lattice. The team is currently investigating the coherent oscillation of electrons, which could further extend the ability of harnessing light-matter interactions from the THz- to the petahertz-frequency range.More

Solar energy-harvesting 'nanotrees' could produce hydrogen fuel on a mass scale
Researchers at the University of California, San Diego have developed a "3-D branched nanowire array" that they claim could cheaply and cleanly deliver hydrogen fuel on a mass scale. The nanowires, which are made from abundant natural materials such as silicon and zinc oxide, mimic the structure of a forest of trees, with individual vertical "trees" sprouting hundreds of nano-sized "branches." Like forests, this structure maximizes the amount of solar energy that can be captured, with the vertical structures trapping and absorbing the light, while the flat surfaces reflect it. The work is described in the journal Nanoscale. More

National Society of Black Physicists jobs board postings
Entrepreneurship for Scientists and Engineers in East Africa
Director, South African Astronomical Observatory
Student Essay Contest - New Frontiers in Astronomy and Cosmology
International Research Grant Competition - New Frontiers in Astronomy and Cosmology
Assistant Editor, Physical Review Letters
Assistant Professor of Physics - University of Wisconsin, River Falls
Marshall REU in Scientific Computing
PostDoc Space Telescope Science Institute
Professor and Director of Science and Technology
REU Program for Community College Students at Texas A&M — Commerce
Research in Sustainable Energy for sub-Saharan Africa
Yale University Center for Research on Interface Structure and Phenomena Postdoctoral Fellow
Iowa State University REU Non-Equilibrium Materials Research Experience for Undergraduates
Iowa State University REU National Science Foundation Engineering Research Center for Biorenewable Chemicals
Iowa State University REU Biogeosciences Research Experiences for Undergraduates
Iowa State University REU Wind Energy Science, Engineering and Policy
Iowa State University REU Microscale Sensing Actuation and Imaging
Iowa State University REU Science Undergraduate Laboratory Internship
Notre Dame Physics REU Program
Jack E. Crow Postdoctoral Fellowship at National High Magnetic Field Laboratory
Iowa State University REU Interdisciplinary Research and Education Emerging Interface Technologies

Latest research from Europhysics Letters
IOP Journal
Disorder-induced Limited Path Percolation

Electrical characteristics of monofilaments in dielectric barrier discharge plasma jets at atmospheric pressure

Photon sorters and QND detectors using single photon emitters

Killing spinors for the bosonic string

Classical light analogue of the nonlocal Aharonov-Bohm effectMore

Latest research from Journal of Geophysical Research, Planets
Journal of Geophysical Research, Planets
Morphometric analysis of small-scale lobate scarps on the moon using data from the Lunar Reconnaissance Orbiter

1st detection of O2 1.27 μm nightglow emission at Mars with OMEGA/MEX and comparison with general circulation model predictions

The effect on the lunar exosphere of a coronal mass ejection passage

Measurements of thermal properties of icy Mars regolith analogs

Delayed formation of the equatorial ridge on Iapetus from a subsatellite created in a giant impactMore