Skip to main content

Experiments and calculations allow examination of boron's complicated dance!!

In a study that combines experimental work and theoretical calculations made possible by supercomputers, scientists have determined the nuclear geometry of two isotopes of boron. The result could help open a path to precise calculations of the structure of other nuclei that scientists could experimentally validate.
Researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory, in collaboration with scientists in Germany and Poland, determined the difference in a quantity known as the nuclear charge radius between boron-10 and boron-11. The nuclear charge radius indicates the size of an atomic nucleus -- which often has relatively indistinct edges.
Nuclear charge radii are difficult to compute with high precision for atoms much larger than boron because of the sheer number of neutrons and protons whose properties and interactions must be derived from quantum mechanics.
Nuclear theory builds from quantum chromodynamics (QCD), a set of physical rules that apply to quarks and gluons that compose the protons and neutrons within the nucleus. But trying to solve the nuclear dynamics using QCD alone would be an almost impossible task due to its complexity, and researchers have to rely on at least some simplifying assumptions.
Because boron is relatively light -- with only five protons and a handful of neutrons -- the team was able to successfully model the two boron isotopes on the Mira supercomputer and study them experimentally using laser spectroscopy. Mira is part of the Argonne Leadership Computing Facility (ALCF), a DOE Office of Science User Facility.
"This is one of the most complicated atomic nuclei for which it is possible to arrive at these precise measurements experimentally and derive them theoretically," said Argonne nuclear physicist Peter Mueller, who helped lead the study.
Looking at how the nuclear configurations of boron-11 (11B) and boron-10 (10B) differed involved making determinations at extraordinarily small length scales: less than a femtometer -- one-quadrillionth of a meter. In a counterintuitive finding, the researchers determined that the 11 nucleons in boron-11 actually occupy a smaller volume than the 10 nucleons in boron-10.
To look experimentally at the boron isotopes, scientists at the University of Darmstadt performed laser spectroscopy on samples of the isotopes, which fluoresce at different frequencies. While most of the difference in the fluorescence patterns is caused by the difference in the mass between the isotopes, there is a component in the measurement that reflects the size of the nucleus, explained Argonne physicist Robert Wiringa.
To separate these components, collaborators from the University of Warsaw and Adam Mickiewicz University in Poznan carried out state-of-the-art atomic theory calculations that precisely describe the complicated dance of the five electrons around the nucleus in the boron atom.
"Earlier electron scattering experiments couldn't really say for sure which was bigger," Wiringa said. "By using this laser spectroscopy technique, we're able to see for certain how the extra neutron binds boron-11 more closely."
The good agreement between experiment and theory for the dimensions of the nucleus allows researchers to determine other properties of an isotope, such as its beta decay rate, with higher confidence. "The ability to perform calculations and do experiments go hand-in-hand to validate and reinforce our findings," Mueller said.
The next stage of the research will likely involve the study of boron-8, which is unstable and only has a half-life of about a second before it decays. Because there are fewer neutrons in the nucleus, it is much less tightly bound than its stable neighbors and is believed to have an extended charge radius, Mueller said. "There is a prediction, but only experiment will tell us how well it actually models this loosely bound system," he explained.
Story Source:
Materials provided by DOE/Argonne National Laboratory. 
Note: Content may be edited .

Comments

Post a Comment

Popular posts from this blog

Major surgery associated with small, long term decline in brain functioning

Major surgery is associated with a small long-term decline in cognitive functioning -- equivalent, on average, to less than five months of natural brain ageing, finds a study in  The BMJ  today. But the odds of substantial cognitive decline also increase after surgery -- approximately doubling -- although the likelihood of this is much lower than after admission to hospital for a medical condition, the findings show. Cognitive decline is the gradual loss of brain functioning that occurs with ageing. It often starts decades before the conventional definition of old age and accelerates with ageing and the presence of an increasing number of underlying health conditions. Certain health issues, such as stroke, can lead to a large "step change" in cognitive decline, and there have been concerns that surgery might also do this, with some patients refusing beneficial surgical procedures as a result, say the researchers. Few previous studies have looked at the potential im...
Post a Comment
Read more

Dark matter may be older than the Big Bang

Dark matter, which researchers believe make up about 80% of the universe's mass, is one of the most elusive mysteries in modern physics. What exactly it is and how it came to be is a mystery, but a new Johns Hopkins University study now suggests that dark matter may have existed before the Big Bang. The study, published August 7 in  Physical Review Letters , presents a new idea of how dark matter was born and how to identify it with astronomical observations. "The study revealed a new connection between particle physics and astronomy. If dark matter consists of new particles that were born before the Big Bang, they affect the way galaxies are distributed in the sky in a unique way. This connection may be used to reveal their identity and make conclusions about the times before the Big Bang too," says Tommi Tenkanen, a postdoctoral fellow in Physics and Astronomy at the Johns Hopkins University and the study's author. While not much is known about its origins,...
Post a Comment
Read more

Scientists challenge notion of binary sexuality with naming of new plant species

A collaborative team of scientists from the US and Australia has named a new plant species from the remote Outback. Bucknell University biology postdoctoral fellow Angela McDonnell and professor Chris Martine led the description of the plant that had confounded field biologists for decades because of the unusual fluidity of its flower form. The discovery, published in the open access journal  PhytoKeys , offers a powerful example of the diversity of sexual forms found among plants. The new species of bush tomato discovered in remote Australia provides a compelling example of the fact that sexuality among Earth's living creatures is far more diverse -- and interesting -- than many people likely realize. Bucknell University postdoctoral fellow Angela McDonnell and biology professor Chris Martine led the study following an expedition last year to relocate populations of the new plant, which were first noted by Australian botanists during the 1970s. Herbarium specimens from th...
Post a Comment
Read more