Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nuclear Masses Measured to within a Hair’s Precision

06.05.2009
MSU researchers have made precise mass measurements of four such nuclei, 68-selenium, 70-selenium, 71-bromine and an excited state of 70-bromine. The results may make it easier to understand X-ray bursts, the most common stellar explosions in the galaxy.

No one likes to say exactly how much they weigh. Rare atomic nuclei are similarly coy, obviously not because of their own volition, but rather because they are exceedingly difficult to produce and, while they exist, very short-lived and difficult to corral and accurately measure.

Now, MSU researchers have made precise mass measurements of four such nuclei, 68-selenium, 70-selenium, 71-bromine and an excited state of 70-bromine (yes, a nucleus weighs measurably more when it is excited because of Einstein’s famous E=mc2 declaration). The results may make it easier to understand X-ray bursts, the most common stellar explosions in the galaxy.

X-ray bursts are spectacular runaway thermonuclear reactions on neutron stars that release vast amounts of energy in a short period of time. In just 10 seconds, an X-ray burst might release as much energy as our sun does in one month. Such explosions occur in binary systems where a neutron star and a second donor star orbit each other. The donor star rains hydrogen and helium onto the surface of the neutron star. When enough of this material accumulates, nuclear fusion reactions begin, dramatically increasing temperature to nearly 2 billion degrees Fahrenheit, which is about 10,000 times hotter than the surface of the sun. This temperature spike gives rise to the explosion and eventually to what’s known as the rapid proton capture nucleo-synthesis-process, or rp-process.

The rp-process occurs when a seed nucleus in a super-hot stellar environment begins capturing protons in quick succession, piling them up until the nucleus cannot hold any more. The nucleus then spits out some energy, turning a proton into a neutron, which allows the piling on to start anew.

The rp-process is roughly analogous to stacking blocks one after the other. Eventually the stack gets sufficiently tall and unsteady that the blocks fall into a more compact and stable jumble. If the stacking continues on top of this pile, eventually a new jumbled shape will be created when the blocks fall down a second time. In time, this repeated stacking and tumbling will create a slew of new increasingly larger piles, just as the successive capture and decay during the rp-process is thought to create many heavy elements, possibly up to tellurium, stable versions of which have 52 protons and anywhere from 70 to 74 neutrons.

The MSU team, including nuclear science doctoral student Josh Savory, were interested in four atomic nuclei because they represent a pause button of sorts during the rp-process. Normally the capture-decay sequence that creates new elements happens in a blink of an eye, in a matter of seconds or less. However it takes time, perhaps 30 seconds or more, for selenium-68 and a few similar nuclei to decay. It’s possible these waiting points can be bypassed if two protons are captured instead of one. Precise mass measurements help to refine theoretical models that explain whether or not these waiting points are bypassed and in general, just how fast nuclear reactions proceed during X-ray bursts. This information, in turn, helps researchers predict and explain just how much of each of the various elements are produced during the rp-process.

The experiment, conducted by Savory and several colleagues, used NSCL’s Low Energy Beam and Ion Trap facility, LEBIT, to make the mass measurements of the four nuclei. LEBIT uses a technique known as Penning trap mass spectrometry to perform these measurements. (A physics 101 aside: Weight and mass are often confused. Weight of matter is entirely dependent upon the strength of gravity while the mass of matter is constant. Someone who weighed 180 pounds on Earth would weigh just 30 pounds on the moon, which exerts a much more modest gravitational pull. That same person’s mass would be the same on Earth, the moon or, with few exceptions, anywhere in the universe. The equation is w (weight) = g (gravity) X m (mass)).

LEBIT takes isotope beams traveling at roughly half the speed of light and carefully slows and stops the isotopes for highly accurate mass measurement. MSU is home to the only physics lab in the world capable of performing such measurements on isotopes produced by fast beam fragmentation, a technique that allows for the production of extremely rare nuclei not normally found on Earth.

The MSU team measured the masses to a level of precision as high as 1 part per 100 million (for 68-selenium) and with an improved precision as large as 100 times (for 71-bromine) in comparison to previous such measurements.

“As an analogue, think of a scale precise enough to see how your weight changes when you pluck just one hair out of your head,” said Savory, lead author of a paper describing the results which appears in Physical Review Letters.

Geoff Koch | Newswise Science News
Further information:
http://www.nscl.msu.edu

More articles from Physics and Astronomy:

nachricht A 100-year-old physics problem has been solved at EPFL
23.06.2017 | Ecole Polytechnique Fédérale de Lausanne

nachricht Quantum thermometer or optical refrigerator?
23.06.2017 | National Institute of Standards and Technology (NIST)

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>