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Showing posts with the label Atomic nuclei

Unraveling the Enigmatic Conundrum: Deciphering the Intricacies of the Cosmological Constant Problem at the Nexus of Quantum Field Theory, General Relativity, and Cosmology

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The problem of the cosmological constant has perplexed physicists for decades, presenting a formidable challenge in our understanding of the fundamental nature of the universe. It stems from a deep conundrum concerning the nature of vacuum energy and its implications for the dynamics of cosmic expansion. To fully appreciate the intricacies of this problem, one must delve into the realms of quantum field theory, general relativity, and cosmology, as these domains intertwine in a complex interplay of concepts and mathematical formalism. In the realm of quantum field theory, the vacuum is not an empty void, but a seething sea of fluctuating fields. These fields, governed by the principles of quantum mechanics, give rise to virtual particles that pop in and out of existence, constantly interacting and influencing the behavior of the vacuum. As a consequence, the vacuum energy is expected to possess a non-zero value, resulting in what is known as vacuum fluctuations. Enter general relativit...

Coherent Simulation of Correlated Electron Systems using Hole Spins in Germanium Quantum Dots

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Coherent Simulation of Correlated Electron Systems using Hole Spins in Germanium Quantum Dots   Abstract: Simulating condensed matter systems beyond the capabilities of classical computers is a promising avenue for advancing our understanding of quantum phenomena. Quantum dots and donors in semiconductor technology offer a natural platform for implementing quantum simulation. While various material platforms have been explored for studying interacting charge and spin states, the challenge of decoherence has limited the realization of coherent quantum dynamics. In this study, we introduce quantum simulation using hole spins in germanium quantum dots, showcasing extensive and coherent control over multi-spin states in isolated, paired, and fully coupled quantum dots. Specifically, we focus on simulating resonating valence bonds (RVBs) and measure the evolution between singlet product states, which remains coherent over many periods. Additionally, we demonstrate the realization of fou...

Unveiling the Ferricyanide Photo-aquation Pathway through Cutting-Edge Spectroscopy Techniques

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Unveiling the Ferricyanide Photo-aquation Pathway through Cutting-Edge Spectroscopy Techniques Abstract: Reliably identifying short-lived chemical reaction intermediates is crucial to elucidate reaction mechanisms but becomes particularly challenging when multiple transient species occur simultaneously. Here, we report a femtosecond x-ray emission spectroscopy and scattering study of the aqueous ferricyanide photochemistry, utilizing the combined Fe Kβ main and valence-to-core emission lines. Following UV-excitation, we observe a ligand-to-metal charge transfer excited state that decays within 0.5 ps. On this timescale, we also detect a hitherto unobserved short-lived species that we assign to a ferric penta-coordinate intermediate of the photo-aquation reaction. We provide evidence that bond photolysis occurs from reactive metal-centered excited states that are populated through relaxation of the charge transfer excited state. Beyond illuminating the elusive ferricyanide p...

Magnetic Flux Trapping in Hydrogen-Rich High-Temperature Superconductors - Unlocking the Mysteries of Enhanced Performance

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Magnetic Flux Trapping in Hydrogen-Rich High-Temperature Superconductors Unlocking the Mysteries of Enhanced Performance Abstract : Recent discoveries of superconductivity in various hydrides at high pressures have shown that a critical temperature of superconductivity can reach near-room-temperature values. However, experimental studies are limited by high-pressure conditions, and electrical transport measurements have been the primary technique for detecting superconductivity in hydrides. Here we implement a non-conventional protocol for the magnetic measurements of superconductors in a SQUID magnetometer and probe the trapped magnetic flux in two near-room-temperature superconductors H 3 S and LaH 10 at high pressures. Contrary to traditional magnetic susceptibility measurements, the magnetic response from the trapped flux is almost unaffected by the background signal of the diamond anvil cell due to the absence of external magnetic fields. The behaviour of the trapped ...

Laser Cooling - A New Frontier Explored in Anion Cooling

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 Laser Cooling - A New Frontier Explored in Anion Cooling The field of laser cooling has witnessed remarkable advancements in recent years, particularly in the cooling of neutral and positively charged ions. However, one significant area that has remained largely unexplored is the cooling of anions. Breaking new ground in this field, scientists have now achieved laser-induced evaporative cooling of negatively charged molecules, opening up a new frontier of possibilities. Laser cooling is a groundbreaking technique that involves using laser beams to reduce the thermal motion of particles, thereby reaching extremely low temperatures. This method has revolutionized the study of atomic and molecular physics, leading to numerous breakthroughs and enabling researchers to explore quantum phenomena with unprecedented precision. Conventionally, laser cooling techniques have been primarily applied to neutral atoms and positively charged ions due to their comparatively simpler behavior and fa...

Single-Photon Absorption and Emission from a Natural Photosynthetic Complex

Single-Photon Absorption and Emission from a Natural Photosynthetic Complex

Excitonic Topological Order in Imbalanced Electron-Hole Bilayers

 Excitonic Topological Order in Imbalanced Electron-Hole Bilayers Abstract:   Excitonic topological order, arising from the interplay of strong Coulomb interactions and the quantum confinement of charge carriers, has recently emerged as a fascinating avenue for exploring novel quantum phenomena. In this article, we delve into the concept of excitonic topological order in imbalanced electron-hole bilayers. We discuss the underlying principles, experimental observations, and potential applications of this intriguing quantum state.

Signatures of Fractional Quantum Anomalous Hall States in Twisted MoTe2

 Signatures of Fractional Quantum Anomalous Hall States in Twisted MoTe2

Une mesure du CERN met en doute le résultat choquant du boson W

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A 2022 measurement of the mass of the W boson threatened to up end particle physics as we know it, but new results from CERN indicate the standard model was right all along

Cylindrical machine with coil-like vertical structures | ''TOKAMAK DRAWING"

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The exploration of the now-digitized Leonardo Da Vinci notebooks continues to amaze the worldwide scientific community. A few weeks ago, engineers at the California Institute of Technology (Caltech) analyzed a series of drawings that clearly indicated that, two centuries before Newton, the Renaissance artist and polymath had devised experiments to investigate the nature of gravity. This week, a researcher at the Fusion Plasma Physics Department of the Hungarian Centre for Energy Research, Daniel Dunai, has unearthed in yet another trove of Leonardo's documents a sketch depicting what appears to be ... a tokamak. The drawing, which experts have dated from the years 1505-1510, shows a cylindrical machine with coil-like vertical structures, surrounded by poles and wires. An oval shape, coloured a long-faded pink, opens in the middle of the contraption. Half a millennium after the drawing was made, one is tempted to see in this shape and colour the representation of a plasma. But the m...

Inside the Enigmatic Proton, the Most Complicated Thing Imaginable

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  A recent experiment carried out at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility has revealed the radius of the proton’s mass that is generated by the strong force as it glues together the proton’s building block quarks. The result was published on March 29 in the journal Nature . One of the biggest mysteries of the proton is the origin of its mass. It turns out that the proton’s measured mass doesn’t just come from its physical building blocks, its three so-called valence quarks.“If you add up the Standard Model masses of the quarks in a proton, you only get a small fraction of the proton’s mass,” explained experiment co-spokesperson Sylvester Joosten, an experimental physicist at DOE’s Argonne National Laboratory. Over the last few decades, nuclear physicists have tentatively pieced together that the proton’s mass comes from several sources. First, it gets some mass from the masses of its quarks, and some more from their movements. ...

A new nuclear imaging prototype detects tumors’ faint glow

A type of light commonly observed in astrophysics experiments and nuclear reactors can help detect cancer. In a clinical trial, a prototype of an imaging machine that relies on this usually bluish light, called Cerenkov radiation, successfully   captured the presence and location   of cancer patients’ tumors, researchers report April 11 in   Nature Biomedical Engineering . When compared with standard scans of the tumors, the Cerenkov light images were classified as “acceptable” or higher for 90 percent of patients, says Magdalena Skubal, a cancer researcher at Memorial Sloan Kettering Cancer Center in New York City. Cerenkov radiation is generated by high-speed particles traveling faster than light through a material, such as bodily tissue. In Cerenkov luminescence imaging, or CLI, particles released by radiotracers cause the target tissue to vibrate and relax in a way that emits light, which is then captured by a camera. Between May 2018 and March 2020, in the ...

Exposition interne, par contact et externe

  Exposition interne, par contact et externe Les rayonnements ionisants sont capables d’arracher des électrons lorsqu’ils traversent la matière et leurs effets biologiques seront variables selon la dose reçue. Exposition à la radioactivité ou bien exposition aux rayonnements ionisants? Pour l’homme de la rue comme le patient, c’est l’exposition à ces rayonnements qui importe davantage que leur origine, une question laissée aux physiciens. La radioactivité émet des rayonnements mais elle n’est pas la seule ! Certes nous sommes soumis aux rayons de l’uranium des roches, du carbone-14 de l’atmosphère, aux émanations du radon, aux retombées des essais atomiques, de Tchernobyl et de Fukushima. Mais nous subissons aussi la pluie de particules du rayonnement cosmique qui bombardent l’atmosphère et ne sont pas d’origine radioactive. Les rayons X, ceux des appareils de radiothérapies non plus. Il y a deux principaux types d’expositions : internes et externes. Dans le cas de l’exposition int...

Quarks et leptons Les constituants fondamentaux de la matière

Etats d'énergie du noyau - Analogie avec l'atome : des états d'énergie bien définis

  Etats d'énergie du noyau - Analogie avec l'atome : des états d'énergie bien définis. Les noyaux sont a priori très différents des atomes. Cent mille fois plus petits, ils sont plus complexes. La matière nucléaire est compacte alors que l'espace atomique est essentiellement constitué de vide. Pourtant noyaux et atomes présentent des traits communs. Quand le noyau se trouve dans un autre état, il dispose d'un supplément d'énergie. Il retourne à l'état normal (celui de repos maximum) et se débarrasse de son énergie d'excitation en émettant un photon d'énergie caractéristique, appelé photon γ ou g amma . Ces photons sont de même nature que les photons et rayons X émis par les atomes, mais leur énergie est beaucoup plus grande : couramment de l'ordre du million d'électronvolts (MeV ) . Les états d'énergie de la communauté de nucléons assemblée en noyau sont variés. Tout d'abord, on observe, comme dans l'atome, l'existence...

The atomic nucleus - The heart of the atom

  Www.karam-ouharou.blogspot.com The atomic nucleus The heart of the atom Almost all matter in the Universe is concentrated within atomic nuclei. Some 100,000 times smaller than the atom, they contain 4,000 times more mass than their orbiting electrons. All nuclei are made up of neutrons and protons, collectively known as nucleons, which play similar roles in maintaining the structure of the nucleus. Whereas electrons can be said to be ‘fundamental’ (or indivisible) particles in their own right, nucleons are made up of quarks , the smallest known units of matter, and as a result are not considered to be fundamental particles. The existence of quarks has imposed itself since the 1970s. In the field of nuclear physics which is that of radioactivity, the habit before was to consider the nucleons as the elementary constituents of the nucleus. For simplicity, we will keep this convention, referring to the internal structure of nucleons and quarks only when necessary.Howev...

La représentation classique d’un noyau

 Www.karam-ouharou.blogspot.com Le noyau atomique Le noyau, cœur de l'atome Toute la matière, ou presque, se retrouve concentrée dans de minuscules noyaux 100000 fois plus petits que l'atome, mais environ 4000 fois plus lourds que le cortège de leurs électrons. Les noyaux sont constitués de protons et de neutrons , deux espèces de particules qui jouent un rôle très similaire dans la matière nucléaire. L'habitude est de regrouper protons et neutrons sous l’ appellation commune de « nucléons ». Alors que l’électron peut être considéré comme un corpuscule élémentaire, les protons et neutrons qui sont constitués de corpuscules plus petits, les quarks , ne le sont pas. L'existence des quarks s'est imposée depuis les années 1970. Dans le domaine de la physique nucléaire qui est celui de la radioactivité, l’habitude était de considérer les nucléons comme les constituants élémentaires du noyau. Pour simplifier, nous conserverons cette convention, ne faisan...

Ordres de grandeur - Prj. 1 - Physique atomique - Confé. Dr. Karam Ouharou

O rdres de grandeur - Confé. Dr. Karam Ouharou à laboratoire d'Annecy de physique des particules   L’atome et plus encore le noyau appartiennent au monde de l’infiniment petit. Ils sont difficiles à appréhender pour le profane. Les unités et ordres de grandeur auxquels nous sommes habitués n’ont plus cours. Les chiffres dont il est question, grands ou petits, deviennent vite faramineux. Voici quelques points de repères. Les dimensions : Les rayons des atomes sont de l’ordre du dix milliardième de mètre. La longueur d’une file d’un milliard d'atomes serait seulement de 20 cm. Un proton est cent mille fois plus petit. La même file composée de protons ne mesurerait que deux microns, deux millièmes de millimètre. Les noyaux sont un peu plus gros, mais guère plus. Les vitesses et le temps : Rien ne va plus vite que la lumière dans le vide. La lumière met 8 minutes pour venir du Soleil à 299 792,458 km /s. Les électrons d'un atome sont loin d'être aussi rapides...

Measure Masses of Exotic Indium Nuclei

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Atomic nuclei have only two ingredients, protons and neutrons, but the relative number of these ingredients makes a radical difference in their properties. Certain configurations of protons and neutrons, with ‘magic numbers’ of protons or neutrons arranged into filled shells within the nucleus, are more strongly bound than others. The rare nuclei with complete proton and neutron shells, which are termed doubly magic, exhibit particularly enhanced binding energy and are excellent test cases for studies of nuclear properties. The new theoretical calculations and experimental results from the ISOLTRAP team shed light on one of the most iconic doubly magic nuclei: tin-100. With 50 protons and 50 neutrons, tin-100 is of particular interest for studies of nuclear properties because, in addition to being doubly magic, it is the heaviest nucleus comprising protons and neutrons in equal number — a feature that gives it one of the strongest beta decays, in which a positron is em...