![]() At the Cyclotron Institute of Texas A&M University, researchers studied the reaction between neon-20 and alpha particles using a thick helium target and a neon-20 beam. The identification and the study of states analogous to the Hoyle state in heavier nuclei can provide a test for the existence of alpha condensates in nuclear matter. Rather, it's a state of nuclear matter that can be found in other nuclei under similar conditions. Finding states analogous to the carbon-12 Hoyle state in heavier nuclei will show that the Hoyle state is not a lucky occurrence in carbon-12. These features can be explained by describing carbon as a diluted gas of alpha particles, implying the existence of a new state of nuclear matter analogous to the well-known Bose-Einstein condensate for molecules. The carbon-12 Hoyle state also has peculiar characteristics. ![]() In fact, it's thanks to this state that carbon-12, the key element for life as we know it, could be formed in the early universe. The existence of the Hoyle state in carbon-12 is very important. Could analogous states exist in other isotopes like oxygen-16 and neon-20? Nuclear researchers at Texas A&M University indicated a state analogous to the Hoyle state exists in oxygen-16. Examples are the ground state of beryllium-8 and the famous carbon-12 "Hoyle" state, named for Fred Hoyle who first postulated its existence to explain the production of carbon in stars. When the nucleus gets nearly enough energy to disintegrate into alpha particles, the alpha particles can arrange themselves in the lowest possible quantum energy level, forming a Bose-Einstein condensate. Two protons and two neutrons in a nucleus can cluster together to form alpha particles. In the future, precision spectroscopic measurements at low energies may well lead to fundamental discoveries, such as new physics beyond the standard model,” explains Professor Hänsch.Nuclei in their lowest energy states (ground state) are composed of neutrons and protons. ![]() “I have always been fascinated by laser spectroscopy of exotic atoms, such as muonic helium, because we can test the laws of quantum physics under conditions that have not been explored before. This agreement also constrains several beyond-standard-model theories proposed to explain the proton-radius puzzle in line with recent determinations of the proton charge radius, and establishes spectroscopy of light muonic atoms and ions as a precise tool for studies of nuclear properties. It provides a benchmark for few-nucleon theories, lattice quantum chromodynamics and electron scattering. The new measurement of the 2S-2P Lamb shift resonance in muonic helium-4 ions by laser spectroscopy yields a root-mean-square charge radius of the α particle of 1.67824(83) femtometers, in excellent agreement with the value from electron scattering, but by a factor of 4.8 more precise. An accurate measurement of the alpha particle charge radius has gained much interest since the discovery of the proton radius puzzle, where laser spectroscopy of muonic hydrogen and ordinary hydrogen gave differing results for the charge radius of the proton. Shifts of atomic energy levels due to the finite size of the nucleus are dramatically magnified in muonic atoms, so that laser spectroscopy can be used to investigate the nuclear structure with high precision. Even though the alpha particle consists of two protons and two neutrons, it is even smaller than the deuteron, which contains only one proton and one neutron. The alpha particle is the smallest atomic nucleus after the proton, the nucleus of the hydrogen atom. ![]() ![]() The charge radius of simple nuclei provide an important testing ground for nuclear theory. Other former MPQ doctoral students in the collaboration include Aldo Antognini, Mark Diepold, and Tobias Nebel. The spokesman, Randolf Pohl, now Professor at the University of Mainz, has been a staff scientist at the MPQ during the time of the experiment, and the first author Julian Krauth, who reported on this experiment as part of his doctoral thesis with Professor Hänsch, has played a central role in coordinating the theoretical interpretation of the experimental data. (source: Ryan Allen MS, Second Bay Studios, Santa Barbara, CA, USA)ĬREMA has many ties to the Laser Spectroscopy Division at the Max-Planck-Institute of Quantum Optics in Garching. The light electron is replaced by much heavier muon. Artist’s view of a measurement of the charge radius of the alpha particle by laser spectroscopy of helium ions. ![]()
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