(Press-News.org) OAK RIDGE, Tenn., Oct. 23, 2012 -- Researchers at the Department of Energy's Oak Ridge National Laboratory have found that nitrogen atoms in the compound uranium nitride exhibit unexpected, distinct vibrations that form a nearly ideal realization of a physics textbook model known as the isotropic quantum harmonic oscillator.
In the experiment on the uranium nitride crystal -- with each of the light nitrogen atoms centered in a cage of heavier uranium atoms -- neutron scattering at ORNL's Spallation Neutron Source (SNS) revealed an unexpected series of distinct and evenly spaced oscillations: The nitrogen atom vibrates like a molecular-level ball on a spring.
"Students of physics are familiar with this idealized quantum 'mass on a spring,' but it is very unexpected to find such a precise literal version of this theoretical model in a real experiment," said Steve Nagler, director of ORNL's Quantum Condensed Matter Division of the Neutron Sciences Directorate and a co-author on the paper, published in the journal Nature Communications.
The researchers were using the intense neutron beams of the SNS to examine the magnetic properties of a single crystal of uranium nitride when they noticed the signatures of quantum oscillations. The researchers' technique -- neutron scattering -- is a tool commonly used to measure conventional quantized sound waves, or "phonon excitations" that occur at low frequencies. The measurements at SNS, however, probed higher frequencies well above the "phonon cutoff".
The new data, obtained using SNS's wide angular-range chopper spectrometer (ARCS) and fine-resolution Fermi chopper spectrometer (SEQUOIA) instruments, revealed up to 10 equally spaced energy levels corresponding to oscillations of individual nitrogen atoms in different quantum states. The team was "astonished" to find this series of high-energy vibrational modes in uranium nitride -- particularly in an experiment that originally set out to investigate magnetism in the material.
"We learn about the quantum harmonic oscillator in undergraduate physics courses, but you never believe you will find such a good example in nature," said Adam Aczel, a postdoctoral fellow within the Quantum Condensed Matter Division and lead author on the paper.
Uranium nitride is a material of interest in that it is being considered as a fuel for the next generation of more efficient nuclear power reactors. The phenomena observed at SNS could lend valuable insight into the material's performance and behavior as a nuclear fuel.
The SNS is the world's most powerful pulsed neutron source with a suite of unique, specialized instruments in its scientific user facility for the study of advanced materials. The uranium nitride research team combined data from ARCS and SEQUOIA with computational models to better understand their findings. The crystal of uranium nitride was provided by the Canadian Neutron Beam Centre (CNBC) of the National Research Council of Canada.
INFORMATION:
The team includes Aczel, Nagler, Garrett Granroth, Doug Abernathy, Greg MacDougall, G.D. Samolyuk and Malcolm Stocks of ORNL and W.J.L. Buyers of CNBC at Chalk River.
This research was supported as part of the Center for Defect Physics, an Energy Frontier Research Center funded by the DOE Office of Science.
The Spallation Neutron Source is an Office of Science User Facility operated for the DOE Office of Science by Oak Ridge National Laboratory.
ORNL is managed by UT-Battelle for the DOE Office of Science. DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov.
Image: http://www.ornl.gov/info/press_releases/photos/UN_QHOdata200.jpg
Caption: A "nearly ideal realization" of a physics textbook model: Bands of scattered neutrons (colors at top) correspond to energy levels quantized in 50 meV lumps (bottom).
NOTE TO EDITORS: You may read other press releases from Oak Ridge National Laboratory or learn more about the lab at http://www.ornl.gov/news. Additional information about ORNL is available at the sites below:
Twitter - http://twitter.com/oakridgelabnews
RSS Feeds - http://www.ornl.gov/ornlhome/rss_feeds.shtml
Flickr - http://www.flickr.com/photos/oakridgelab
YouTube - http://www.youtube.com/user/OakRidgeNationalLab
LinkedIn - http://www.linkedin.com/companies/oak-ridge-national-laboratory
Facebook - http://www.facebook.com/Oak.Ridge.National.Laboratory
Neutron experiments give unprecedented look at quantum oscillations
2012-10-23
[Attachments] See images for this press release:
ELSE PRESS RELEASES FROM THIS DATE:
Puppies don't pick up on yawns
2012-10-23
VIDEO:
Video clip shows puppy with familiar experimenter and unfamiliar experimenter.
Click here for more information.
Do you get tired when others yawn? Does your dog get tired when you yawn? New research from Lund University establishes that dogs catch yawns from humans. But not if the dogs are too young. The study, published in Springer's journal Animal Cognition, found that, like humans, dogs show a developmental trend in susceptibility to contagious yawning.
While dogs ...
Lifting weights protects against metabolic syndrome
2012-10-23
Philadelphia, Pa. (October 23, 2012) - People who lift weights are less likely to have metabolic syndrome—a cluster of risk factors linked to heart disease and diabetes, reports a study in the October issue of The Journal of Strength and Conditioning Research, official research journal of the National Strength and Conditioning Association (NSCA). The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.
"Lifting weights may play a role in reducing the prevalence and risk of metabolic syndrome among U.S. adults," according to the study ...
Nanofibrillar cellulose film to ease performing medical tests
2012-10-23
Researchers at Aalto University in Finland have succeeded in developing a durable and affordable nanofibrillar cellulose film platform to support medical testing. New environmentally friendly, reliable nanofibrillar cellulose (NFC) platforms are more diverse than plastic films. New film can be made, for instance, hydrophobic, hydrophilic and the electric charge can be changed. This will enhance the possibility of conducting thousands of different medical tests at home or in physicians' receptions instead of waiting for results from laboratories.
A platform is coated with ...
Migratory birds can spread haemorrhagic fever
2012-10-23
A type of haemorrhagic fever that is prevalent in Africa, Asia, and the Balkans has begun to spread to new areas in southern Europe. Now Swedish researchers have shown that migratory birds carrying ticks are the possible source of contagion. The discovery is being published in the US journal Emerging Infectious Diseases.
Crimean-Congo Haemorrhagic fever is a serious disease that begins with influenza-like symptoms but can develop into a very serious condition with high mortality (30%). The disease occurs in Africa, Asia, and the Balkans but it has recently started to ...
Low adoption by large hospital ICUs of catheter-associated urinary tract infection precautions
2012-10-23
NEW YORK –Hospital size matters when it comes to intensive care units (ICUs) adopting even the most routine prevention policies for catheter-associated urinary tract infections (CAUTI), according to a new study from researchers at Columbia University School of Nursing, published this month in the American Journal of Infection Control. The study found that large hospitals -- those with more than 500 beds --had a 1.5 higher average rate of CAUTI than hospitals with 500 beds or less. Since larger hospitals, particularly teaching hospitals treat patients who are often sicker, ...
Tiny pores in graphene could give rise to membranes
2012-10-23
CAMBRIDGE, Mass. — Much has been made of graphene's exceptional qualities, from its ability to conduct heat and electricity better than any other material to its unparalleled strength: Worked into a composite material, graphene can repel bullets better than Kevlar. Previous research has also shown that pristine graphene — a microscopic sheet of carbon atoms arranged in a honeycomb pattern — is among the most impermeable materials ever discovered, making the substance ideal as a barrier film.
But the material may not be as impenetrable as scientists have thought. By engineering ...
Are schizophrenia and autism close relations?
2012-10-23
Autism Spectrum Disorders (ASD), a category that includes autism, Asperger Syndrome, and Pervasive Developmental Disorder, are characterized by difficulty with social interaction and communication, or repetitive behaviors. The U.S. Centers for Disease Control and Management says that one in 88 children in the US is somewhere on the Autism spectrum — an alarming ten-fold increase in the last four decades.
New research by Dr. Mark Weiser of Tel Aviv University's Sackler Faculty of Medicine and the Sheba Medical Center has revealed that ASD appears share a root cause with ...
NASA sees active region on the sun emit another flare
2012-10-23
VIDEO:
Video of the Oct. 22, 2012, solar flare as captured by NASA's Solar Dynamics Observatory in the 131 and 304 Angstrom wavelengths. LINK TO HIGHEST RESOLUTION VIDEO: ...
Quasar may be embedded in unusually dusty galaxy
2012-10-23
Hubble astronomers have looked at one of the most distant and brightest quasars in the universe and are surprised by what they did not see: the underlying host galaxy of stars feeding the quasar. The best explanation is that the galaxy is shrouded in so much dust that the stars are completely hidden everywhere. Astronomers believe that the James Webb Space Telescope will reveal the galaxy.
All but the very first galaxies contain some dust—the early universe was dust-free until the first generation of stars started making dust through nuclear fusion. As these stars aged ...
Is declining medical imaging use driving up hospital stays and medical costs?
2012-10-23
A new report by the Harvey L. Neiman Health Policy Institute shows that the length of the average hospital stay in the United States has increased at the same time as use of medical imaging scans has declined. It is unclear if the trends are related, but potentially important, as hospital admissions are among the largest, and fastest growing, health care costs. More research is needed to assess the potential negative impact of government and private insurer imaging reductions on overall medical costs and patient safety.
"Lawmakers, regulators and medical professionals ...