Golden Science Nuggets
Magicity ends with Oxygen Isotopes
A recent experiment performed at the National Superconducting Cyclotron Laboratory (NSCL) provided important insight into one of the significant questions about the structure of the most neutron-rich nuclei. It has been known for several years that the largest number of neutrons that an oxygen nucleus can hold is 16 while the neighboring element fluorine can hold at least 22. This surprising difference is somewhat unexpected based on extrapolations of the nuclear structure observed for the stable oxygen and other light isotopes. In the new work, the experimenters showed that the excitation energy of the first excited state in 24O was surprisingly high, indicative of a large energy gap between nuclear orbitals or that 16 represents a so-called closed shell of neutrons. The new work combined with the well-known feature of the nuclear shell model that the binding energy of nucleons drops significantly for nucleons added to a nucleus with a completed filled shell (so-called magic or closed-shell nuclei) leads immediately to loss of stability for oxygen isotopes heavier than 24O. More
Researchers explore a new region of deformation in the nuclear chart
A new result from the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University yields clues to a new region of deformation in the nuclear chart. The NSCL provides beams of rare and exotic nuclei that have not been studied before. While the vast majority of nuclei are spherical, it is important to determine the exact shape of new, exotic nuclei. Anomalies in the nuclear structure of nuclei with unusual proton-to-neutron ratios sometimes leads to usual shapes which then offers important challenges to our understanding of atomic nuclei. More
Determining ground-state wave functions in light, stable and exotic nuclei
The nuclear shell model, analogous to the atomic electron shell model, is perhaps the most important and general model for calculating a wide range of nuclear properties. A stringent test that has been developed over many years is to compare the measured probability for the transfer of a single neutron in a direct reaction to the probability predicted using the shell model wave functions of the nuclei. This ratio is called the spectroscopic factor and provides a simple measure of how well the shell model can describe a given nuclear state. Recently, scientists at the National Superconducting Cyclotron Lab (NSCL) on the campus of Michigan State University produced a consistent and systematic set of spectroscopic factors from a wide range of data on single neutron transfer reactions. More
Constraining the symmetry energy in the nuclear equation of state
The nuclear equation of state is a thermodynamic description of the average behavior of a large volume of nuclear matter in exact analogy to the equation of state of a gas or any other phase of matter. The nuclear symmetry energy is a component of the nuclear equation of state that describes the variation of the nuclear binding energy as a function of proton (Z) and neutron (N) numbers. While the range of neutron-to-proton number is relatively small in nuclei, neutron stars are thought to be close to pure neutron matter. In this case the nature and stability of phases within the star, the composition and the thickness of its inner crust, the frequencies of vibrations of the crust and its radius, among other properties, depend strongly on the symmetry energy and its density dependence. More
The beginning of CAESAR's reign
A novel and extremely high-efficiency photon detector was just completed at the National Superconducting Cyclotron Laboratory (NSCL) with funding by a Major Research Instrumentation (MRI) grant from the NSF. The array of 192 detectors, called CAESAR (for CAESium iodide ARray), incorporates a special scintillator material to detect the gamma rays emitted in nuclear reactions by atomic nuclei that move at more than 30% of the speed of light. As in atomic systems, determining the spectrum of photons from excited nuclear systems provides unprecedented and unique information on their properties. The new detector system will significantly enhances the world-leading scientific program that the NSCL. After the initial tests, the array was used in two experiments and demonstrated its ability to collect dramatically more data on the collision products in significantly less beam time. More
New technique for charge-exchange reactions on rare isotopes
Researchers from the National Superconducting Cyclotron Laboratory (NSCL) on the campus of Michigan State University have developed an important new method to study charge-exchange reactions at intermediate energies using rare isotopes. Charge-exchange nuclear reactions are those in which a proton in one nucleus is exchanged for a neutron in the other nucleus during a fast collision. This nuclear reaction is particularly simple and had been used as an important tool in nuclear structure studies of stable nuclei. More
Key benchmark nucleus produced and studied
Noble gasses with their filled shells of electrons are the benchmarks for atomic theory. Their existence, not discovered until 1898, became a cornerstone in the development of the atomic shell model. The equivalent "benchmarks" in nuclear models are so-called doubly magic nuclei, which have closed shells of protons and neutrons. The few doubly magic nuclei in nature, helium-4, oxygen-16, calcium-40,48 and lead-208 are the starting points for modeling more complex nuclei. Nuclear scientists at the Michigan State University National Superconducting Cyclotron Laboratory (NSCL) have now synthesized a new doubly magic nucleus with special characteristics – tin-100. More
New neutron-rich nuclei support 'island of inversion' theory
Mapping the properties of nuclei at the edge of the nuclear landscape is one of the fundamental pursuits in experimental nuclear science. Even the simple proof of existence of an isotope, which lives only for a fraction of a second, is sufficient to guide theorists in the development a comprehensive model of nuclear matter. Researchers at the Michigan State University National Superconducting Cyclotron Laboratory (NSCL) have succeeded in producing and measuring the production rates of 15 new neutron-rich isotopes never before produced in a laboratory setting. Several of these new, rare isotopes were produced at significantly higher-than-expected rates. The result suggests the existence of a new "island of inversion," a region of isotopes with enhanced stability in a sea of mostly fleeting and unstable nuclei at the edge of the nuclear map. More
Shape transitions and new interactions in neutron-rich nuclei
A new research result from the Michigan State University National Superconducting Cyclotron Laboratory (NSCL) suggests that elongated and squashed atomic nuclei may be more common than previously expected, even in isotopes with so-called magic numbers of protons and/or neutrons. The special, spherical nuclei we find in nature may be the exception rather than the rule. The finding challenges the simple conjecture that the quantum mechanical magic numbers in nuclei, that parallel the magic numbers of electrons in noble gas atoms, remain robust across the entire nuclear chart. More
Diamonds are (still) forever
Radioactive beam facilities of the newest generation can produce beams of rare istopes with rates up to 108 particles per second. In many experiments it would be desirable to track particle positions and measure timing properties of these intense beams on a event-by-event basis. Researchers at the NSCL and MSU's physics department developed a particle detector made from single-crystal diamond that will significantly extend the capabilities of conventional detection technology. The diamond is grown by chemical vapor deposition (CVD) at MSU's Keck Microfabrication Facility.
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Nuclear reaction rates and the production of carbon in stars
Early in their lives, stars with masses a few times that of the sun burn the hydrogen in their cores to make helium, become red giant stars, and then burn that helium to make carbon and oxygen. The standard description predicts stars with a dominantly oxygen, yet light observed in nature appears to indicate carbon rich envelopes.The solution to this puzzle may lie in the uncertainties of nuclear reaction rates used in the models. More
Ground state magnetic moment of Potassium-35
Although Potassium-35 lies very near the proton drip line, its magnetic properties still remain similar in nature to those nuclei nearest the valley of stability. More
g-factor of Sulfur-38 and Sulfur-40 and the transition to nuclear deformation
The g-factors of the neutron-rich sulfur isotopes Sulfur-38 and Sulfur-40 were measured. This was the first application of the High Velocity Transient Field (HVTF) method developed in collaboration with researchers from the Australian National University. More
Magnetic moment of Copper-57 and breaking of the Nickel-56 double-magic core
The magnetic dipole moment of Copper-57 was deduced by application of the Nuclear Magnetic Resonance technique, which is a similar technique to Magnetic Resonance Imaging used in the hospitals for functional diagnostics, but improves on sensitivity by a million*billion times using radiation-detection methods. More
Rare-Ion Beams Brought to Rest
A team at the NSCL has succeeded in bring beams of rare, short-lived isotopes traveling at approximately one-half the speed of light (330 million mph) to rest. Once captured and thermalized in a buffer gas, the buffer gas was stripped off and the ions were sent on to an ion trap for mass measurements carried out with extreme precision. More
Towards describing atomic nuclei beyond the drip line
A new version of the Continuum Shell Model simultaneously describes neutron-bound and neutron-unbound states in oxygen isotopes. More
First observation of Germanium-60 and Selenium-64
Two new proton-rich isotopes, Germanium-60 and Selenium-64, were observed for the first time. More
First Penning trap mass measurement of Calcium-38
This measurement marks not only LEBIT's first resonance of an instable nucleus, it is the first Penning trap mass measurement of the Calcium-38 nuclide and it is the first Penning trap mass measurement of any nucleus at a fragmentation facility. More
Diamonds are forever
Researchers at the NSCL and MSU's physics department developed a particle detector made from single-crystal diamond that will significantly extend the capabilities of conventional detection technology. More
Production yields of rare isotopes from projectile fragmentation of Calcium-40 and Calcium-48
A set of recent experiments at the NSCL has demonstrated the production of almost twice as many isotopes, most of which are neutron-rich. More
New reaction discovered: Hitting two nuclear gulls with one bullet
When a neutron-rich projectile reacts with a light nuclear target, the knockout of two protons occurs as a direct reaction. More
Half-life of Nickel-78
The half-life of Nickel-78 offers a glimpse at the origin of precious metals in nature. More
Fewer neutrons than expected
A single neutron was removed from the surface of the atomic nucleus Argon-32. Surprisingly few neutrons occupy the outmost shell of this rare isotope. More
Magic nucleus Silicon-42
A collaboration of researchers from Florida State University, the NSCL, Lawrence Berkeley National Laboratory, and the University of Surrey (UK) used rare isotope beams from the Coupled Cyclotron Facility to demonstrate the magicity of Silicon-42. More
