News

Puzzling sizes of extremely light calcium isotopes

When examined closely, FRIB researchers found radii vary in unique ways, reflecting the intricate behavior of protons and neutrons inside the nucleus.

Credit: Michigan State University

When examined closely, FRIB researchers found radii vary in unique ways, reflecting the intricate behavior of protons and neutrons inside the nucleus.

Credit: Michigan State University

Close

Michigan State University researchers have measured for the first time the nuclei of three protein-rich calcium isotopes, according to a new paper published in Nature Physics.

advertisement

One of the most fundamental properties of the nucleus is its size. The nuclear radius generally increases with the number of proton and neutron constituents. However, when examined closely, the radii vary in unique ways, reflecting the intricate behavior of protons and neutrons inside the nucleus.

Of particular interest is the variation of the charge radii of calcium isotopes. They exhibit a peculiar behavior with calcium-48 having almost the same radius as calcium-40, a local maximum at calcium-44, a distinct odd-even zigzag pattern, and a very large radius for calcium-52. Although the pattern has been partially explained (gray line in the figure), many existing theories struggle to explain this behavior. Below the lightest stable calcium-40 isotope, the charge radius has been known only for calcium-39, due to the difficulty in producing proton-rich calcium nuclei.

The radius of a calcium nucleus is small, about 0.0000000000000035 meters (or 3.5 femtometers), and the local variation is 200 times smaller still. Moreover, the proton-rich calcium isotopes are rather short-lived. For example, calcium-36 exists for just one tenth of a second. The tiny changes in charge radii of very short-lived isotopes can be measured using the laser spectroscopy technique developed at the BEam COoler and LAser spectroscopy, BECOLA, facility at the National Superconducting Cyclotron Laboratory at Michigan State University.

The research, led by Andrew Miller, NSCL graduate assistant, measured for the first time (red squares in figure) the charge radii of three proton-rich calcium isotopes (with mass numbers A=36, 37, 38). These were found to be much smaller than previous theoretical predictions and present a new puzzle. However, an improved theoretical model with a focus on these present data remarkably reproduces the general trend of radii from calcium-36 all the way to calcium-52 (blue line in figure). This success can be attributed to a better understanding of the peculiar ways in which protons interact with each other at large distances outside the surface of a proton-rich calcium nucleus. The improved understanding of charge radii will impact further developments of a global model of the atomic nucleus.

The laser spectroscopy experiment at BECOLA and the improved nuclear model will play an even more essential role in the determination and interpretation of radii of nuclei at the Facility for Rare Isotope Beams currently under construction at MSU, which will provide unprecedented access to new rare isotopes.

advertisement

Materials provided by Michigan State University . Note: Content may be edited for style and length.

Michigan State University. "Puzzling sizes of extremely light calcium isotopes." ScienceDaily. ScienceDaily, 11 February 2019. .

Michigan State University. "Puzzling sizes of extremely light calcium isotopes." ScienceDaily. www.sciencedaily.com/releases/2019/02/190211140039.htm (accessed February 11, 2019).
Read more on sciencedaily.com
News Topics :
Similar Articles :
Technology
Researchers from Michigan State University and the RIKEN Nishina Center in Japan have discovered eight new rare isotopes, including the heaviest known calcium atom, calcium 60. The illustration shows a plot...
Science
This superconducting cyclotron generates beams of exotic nuclei at RIKEN s Radioactive Isotope Beam Facility in Wako, Japan, where the new calcium nuclei were spotted. RIKEN Physicists in Japan have...
Technology
A magic number is a number of protons or neutrons in the nucleus of an elemental particle that results in much greater stability than that of nuclei with other numbers...
Technology
This instrumentation at Japan s Radioactive Isotope Beam Factory in Wako, Japan, was used in an experiment to create an exotic magnesium isotope. Credit RIKEN Nishina Center for Accelerator Based Science...
Technology
Is there an end to the periodic table Illustration of part of periodic table of elements with four new elements in period 7 called out, with oganesson element specifically highlighted....