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Hollow Atoms
Hollow Atoms (discovered in 1990 by a French team of researchers around Jean-Pierre Briand) are short-lived multiply excited neutral atoms which carry a large part of their Z electrons (Z ... projectile nuclear charge) in high-n levels while inner shells remain (transiently) empty. The hollow atoms are exotic atomic species whose all, or most, electrons lie in excited states, while the innermost shells are empty. These atomic species were first observed during the interaction of highly charged ions with surfaces. population inversion arises for typically 100 femtoseconds during the ''interaction of a slow highly charged ion (HCI) with a solid surface''. Despite this limited lifetime, the formation and decay of a hollow atom can be conveniently studied from ejected electrons and soft X-rays, and the trajectories, energy loss and final charge state distribution of surface-scattered projectiles. For impact on insulator surfaces the potential energy contained by hollow atom may also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HCI Surface Interaction
HCI may refer to: Computing * Happy Computers, an American computer hardware manufacturer * Home Computer Initiative, a United Kingdom government programme to increase computers usage * Host controller interface (other), various computer interfaces * Human–computer interaction, the study of how people interact with computers ** Human-computer interaction (security), the study of how people interact with computers concerning information security * Hyper-converged infrastructure, an IT infrastructure framework for integrating storage, networking and virtualization computing in a data center. Education * Harbord Collegiate Institute, a school in Toronto, Canada * Humberside Collegiate Institute, a school in Toronto, Canada * Hwa Chong Institution, a school in Singapore Science * Highly charged ion * Hot carriers injection, in solid-state electronic devices * Hydrocarbon indicator, in reflection seismology Organizations * Handgun Control, Inc., the former name of the Brady ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atoms
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small, typically around 100 picometers across. They are so small that accurately predicting their behavior using classical physics, as if they were tennis balls for example, is not possible due to quantum effects. More than 99.94% of an atom's mass is in the nucleus. The protons have a positive electric charge, the electrons have a negative electric charge, and the neutrons have no electric charge. If the number of protons and electrons are equal, then the atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively – such atoms are called ions. The electrons of an atom are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Population Inversion
In science, specifically statistical mechanics, a population inversion occurs while a system (such as a group of atoms or molecules) exists in a state in which more members of the system are in higher, excited states than in lower, unexcited energy states. It is called an "inversion" because in many familiar and commonly encountered physical systems, this is not possible. This concept is of fundamental importance in laser science because the production of a population inversion is a necessary step in the workings of a standard laser. Boltzmann distributions and thermal equilibrium To understand the concept of a population inversion, it is necessary to understand some thermodynamics and the way that light interacts with matter. To do so, it is useful to consider a very simple assembly of atoms forming a laser medium. Assume there is a group of ''N'' atoms, each of which is capable of being in one of two energy states: either #The ''ground state'', with energy ''E''1; or #The ''exc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Femtoseconds
A femtosecond is a unit of time in the International System of Units (SI) equal to 10 or of a second; that is, one quadrillionth, or one millionth of one billionth, of a second. For context, a femtosecond is to a second as a second is to about 31.71 million years; a ray of light travels approximately 0.3 μm (micrometers) in 1 femtosecond, a distance comparable to the diameter of a virus.Compared with overview in: Page 3 The word ''femtosecond'' is formed by the SI prefix ''femto'' and the SI unit ''second''. Its symbol is fs. A femtosecond is equal to 1000 attoseconds, or 1/1000 picosecond. Because the next higher SI unit is 1000 times larger, times of 10−14 and 10−13 seconds are typically expressed as tens or hundreds of femtoseconds. * Typical time steps for molecular dynamics simulations are on the order of 1 fs. * The periods of the waves of visible light have a duration of about 2 femtoseconds. = = 2.0 \times 10^~ The precise duration depends on the ener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-rays
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 Picometre, picometers to 10 Nanometre, nanometers, corresponding to frequency, frequencies in the range 30 Hertz, petahertz to 30 Hertz, exahertz ( to ) and energies in the range 145 electronvolt, eV to 124 keV. X-ray wavelengths are shorter than those of ultraviolet, UV rays and typically longer than those of gamma rays. In many languages, X-radiation is referred to as Röntgen radiation, after the German scientist Wilhelm Röntgen, Wilhelm Conrad Röntgen, who discovered it on November 8, 1895. He named it ''X-radiation'' to signify an unknown type of radiation.Novelline, Robert (1997). ''Squire's Fundamentals of Radiology''. Harvard University Press. 5th edition. . Spellings of ''X-ray(s)'' in English include the variants ''x-ray(s)'', ''xray(s)'', and ''X ray(s)''. The most familiar use of X-ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sputtering
In physics, sputtering is a phenomenon in which microscopic particles of a solid material are ejected from its surface, after the material is itself bombarded by energetic particles of a plasma or gas. It occurs naturally in outer space, and can be an unwelcome source of wear in precision components. However, the fact that it can be made to act on extremely fine layers of material is utilised in science and industry—there, it is used to perform precise etching, carry out analytical techniques, and deposit thin film layers in the manufacture of optical coatings, semiconductor devices and nanotechnology products. It is a physical vapor deposition technique. Physics When energetic ions collide with atoms of a target material, an exchange of momentum takes place between them. These ions, known as "incident ions", set off collision cascades in the target. Such cascades can take many paths; some recoil back toward the surface of the target. If a collision cascade reaches the surfac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanostructures
A nanostructure is a structure of intermediate size between microscopic and molecular structures. Nanostructural detail is microstructure at nanoscale. In describing nanostructures, it is necessary to differentiate between the number of dimensions in the volume of an object which are on the nanoscale. Nanotextured surfaces have ''one dimension'' on the nanoscale, i.e., only the thickness of the surface of an object is between 0.1 and 100 nm. Nanotubes have ''two dimensions'' on the nanoscale, i.e., the diameter of the tube is between 0.1 and 100 nm; its length can be far more. Finally, spherical nanoparticles have ''three dimensions'' on the nanoscale, i.e., the particle is between 0.1 and 100 nm in each spatial dimension. The terms nanoparticles and ultrafine particles (UFP) are often used synonymously although UFP can reach into the micrometre range. The term ''nanostructure'' is often used when referring to magnetic technology. Nanoscale structure in biology is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
