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Hydrogen Ion Cluster
A hydrogen molecular ion cluster or hydrogen cluster ion is a positively charged cluster of hydrogen molecules. The hydrogen molecular ion () and trihydrogen ion () are well defined molecular species. However hydrogen also forms singly charged clusters () with ''n'' up to 120. Experiments Hydrogen ion clusters can be formed in liquid helium or with lesser cluster size in pure hydrogen. is far more common than higher even numbered clusters. is stable in solid hydrogen. The positive charge is balanced by a solvated electron. It is formed when ionizing radiation impinges on solid hydrogen, and so is formed in radioactive solid tritium. In natural hydrogen treated with radiation, the positive charge transfers to HD molecules, in preference to , with the ultimate most stable arrangement being HD(HD)+HD. can migrate through solid hydrogen by linking a hydrogen molecule at one end and losing it at the other: + → + . This migration stops once an HD molecule is added resulting in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Molecular Ion
The dihydrogen cation or hydrogen molecular ion is a cation (positive ion) with formula . It consists of two hydrogen nuclei (protons) sharing a single electron. It is the simplest molecular ion. The ion can be formed from the ionization of a neutral hydrogen molecule . It is commonly formed in molecular clouds in space, by the action of cosmic rays. The dihydrogen cation is of great historical and theoretical interest because, having only one electron, the equations of quantum mechanics that describe its structure can be solved in a relatively straightforward way. The first such solution was derived by Ø. Burrau in 1927, just one year after the wave theory of quantum mechanics was published. Physical properties Bonding in can be described as a covalent one-electron bond, which has a formal bond order of one half. The ground state energy of the ion is -0.597 Hartree. Isotopologues The dihydrogen cation has six isotopologues, that result from replacement of one or more ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trihydrogen Ion
The trihydrogen cation or protonated molecular hydrogen is a cation (positive ion) with formula , consisting of three hydrogen nuclei (protons) sharing two electrons. The trihydrogen cation is one of the most abundant ions in the universe. It is stable in the interstellar medium (ISM) due to the low temperature and low density of interstellar space. The role that plays in the gas-phase chemistry of the ISM is unparalleled by any other molecular ion. The trihydrogen cation is the simplest triatomic molecule, because its two electrons are the only valence electrons in the system. It is also the simplest example of a three-center two-electron bond system. History was first discovered by J. J. Thomson in 1911. While studying the resultant species of plasma discharges, he discovered something very odd. Using an early form of mass spectrometry, he discovered a large abundance of a molecular ion with a mass-to-charge ratio of 3. He stated that the only two possibilities were ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solid Hydrogen
Solid hydrogen is the solid state of the element hydrogen, achieved by decreasing the temperature below hydrogen's melting point of . It was collected for the first time by James Dewar in 1899 and published with the title "Sur la solidification de l'hydrogène" (English: On the solidification of hydrogen) in the ''Annales de Chimie et de Physique'', 7th series, vol. 18, Oct. 1899. Solid hydrogen has a density of 0.086 g/cm3 making it one of the lowest-density solids. Molecular solid hydrogen At low temperatures and at pressures up to around 400 GPa, hydrogen forms a series of solid phases formed from discrete H2 molecules. ''Phase I'' occurs at low temperatures and pressures, and consists of a hexagonal close-packed array of freely rotating H2 molecules. Upon increasing the pressure at low temperature, a transition to ''Phase II'' occurs at up to 110 GPa. Phase II is a broken-symmetry structure in which the H2 molecules are no longer able to rotate freely. If the pressure i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tritium
Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus of the common isotope hydrogen-1 (''protium'') contains one proton and zero neutrons, and that of hydrogen-2 (''deuterium'') contains one proton and one neutron. Naturally occurring tritium is extremely rare on Earth. The atmosphere has only trace amounts, formed by the interaction of its gases with cosmic rays. It can be produced artificially by irradiating lithium metal or lithium-bearing ceramic pebbles in a nuclear reactor and is a low-abundance byproduct in normal operations of nuclear reactors. Tritium is used as the energy source in radioluminescent lights for watches, gun sights, numerous instruments and tools, and even novelty items such as self-illuminating key chains. It is used in a medical and scientific setting as a radioacti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antiprismatic Symmetry
In geometry, dihedral symmetry in three dimensions is one of three infinite sequences of point groups in three dimensions which have a symmetry group that as an abstract group is a dihedral group Dih''n'' (for ''n'' ≥ 2). Types There are 3 types of dihedral symmetry in three dimensions, each shown below in 3 notations: Schönflies notation, Coxeter notation, and orbifold notation. ;Chiral: *''Dn'', 'n'',2sup>+, (22''n'') of order 2''n'' – dihedral symmetry or para-n-gonal group (abstract group: ''Dihn''). ;Achiral: *''Dnh'', 'n'',2 (*22''n'') of order 4''n'' – prismatic symmetry or full ortho-n-gonal group (abstract group: ''Dihn'' × ''Z''2). *''Dnd'' (or ''Dnv''), ''n'',2+ (2*''n'') of order 4''n'' – antiprismatic symmetry or full gyro-n-gonal group (abstract group: ''Dih''2''n''). For a given ''n'', all three have ''n''-fold rotational symmetry about one axis (rotation by an angle of 360°/''n'' does not change the object), and 2-fold rotational symme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Symmetry
Molecular symmetry in chemistry describes the symmetry present in molecules and the classification of these molecules according to their symmetry. Molecular symmetry is a fundamental concept in chemistry, as it can be used to predict or explain many of a molecule's chemical properties, such as whether or not it has a dipole moment, as well as its allowed spectroscopic transitions. To do this it is necessary to use group theory. This involves classifying the states of the molecule using the irreducible representations from the character table of the symmetry group of the molecule. Symmetry is useful in the study of molecular orbitals, with applications to the Hückel method, to ligand field theory, and to the Woodward-Hoffmann rules. Many university level textbooks on physical chemistry, quantum chemistry, spectroscopy and inorganic chemistry discuss symmetry. Another framework on a larger scale is the use of crystal systems to describe crystallographic symmetry in bulk materia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Anion
The hydrogen anion, H−, is a negative ion of hydrogen, that is, a hydrogen atom that has captured an extra electron. The hydrogen anion is an important constituent of the atmosphere of stars, such as the Sun. In chemistry, this ion is called hydride. The ion has two electrons bound by the electromagnetic force to a nucleus containing one proton. The binding energy of H− equals the binding energy of an extra electron to a hydrogen atom, called electron affinity of hydrogen. It is measured to be or (see Electron affinity (data page)). The total ground state energy thus becomes . Occurrence The hydrogen anion is the dominant bound-free opacity source at visible and near-infrared wavelengths in the atmospheres of stars like the Sun and cooler; its importance was first noted in the 1930s. The ion absorbs photons with energies in the range 0.75–4.0 eV, which ranges from the infrared into the visible spectrum. Most of the electrons in these negative ions come from the i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Specific Impulse
Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse is exactly proportional to the effective exhaust gas velocity. A propulsion system with a higher specific impulse uses the mass of the propellant more efficiently. In the case of a rocket, this means less propellant needed for a given delta-v, so that the vehicle attached to the engine can more efficiently gain altitude and velocity. In an atmospheric context, specific impulse can include the contribution to impulse provided by the mass of external air that is accelerated by the engine in some way, such as by an internal turbofan or heating by fuel combustion participation then thrust expansion or by external propeller. Jet engines breathe external air for both combustion and by-pass, and therefore have a much higher specific impulse than ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Gravity
The standard acceleration due to gravity (or standard acceleration of free fall), sometimes abbreviated as standard gravity, usually denoted by or , is the nominal gravitational acceleration of an object in a vacuum near the surface of the Earth. It is defined by standard as . This value was established by the 3rd CGPM (1901, CR 70) and used to define the standard weight of an object as the product of its mass and this nominal acceleration. The acceleration of a body near the surface of the Earth is due to the combined effects of gravity and centrifugal acceleration from the rotation of the Earth (but the latter is small enough to be negligible for most purposes); the total (the apparent gravity) is about 0.5% greater at the poles than at the Equator. Although the symbol is sometimes used for standard gravity, (without a suffix) can also mean the local acceleration due to local gravity and centrifugal acceleration, which varies depending on one's position on Earth (see Earth's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Picoampere
The ampere (, ; symbol: A), often shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One ampere is equal to electrons worth of charge moving past a point in a second. It is named after French mathematician and physicist André-Marie Ampère (1775–1836), considered the father of electromagnetism along with Danish physicist Hans Christian Ørsted. As of the 2019 redefinition of the SI base units, the ampere is defined by fixing the elementary charge to be exactly C (coulomb), which means an ampere is an electrical current equivalent to elementary charges moving every seconds or elementary charges moving in a second. Prior to the redefinition the ampere was defined as the current that would need to be passed through 2 parallel wires 1 metre apart to produce a magnetic force of newtons per metre. The earlier CGS system had two definitions of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithium Deuteride
Lithium hydride is an inorganic compound with the formula Li H. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not soluble but reactive with all protic organic solvents. It is soluble and nonreactive with certain molten salts such as lithium fluoride, lithium borohydride, and sodium hydride. With a molar mass of 7.95 g/mol, it is the lightest ionic compound. Physical properties LiH is a diamagnetic and an ionic conductor with a conductivity gradually increasing from at 443 °C to 0.18 Ω−1cm−1 at 754 °C; there is no discontinuity in this increase through the melting point. The dielectric constant of LiH decreases from 13.0 (static, low frequencies) to 3.6 (visible-light frequencies). LiH is a soft material with a Mohs hardness of 3.5. Its compressive creep (per 100 hours) rapidly increases from 100% at 475 °C, meaning that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, and highly combustible. Hydrogen is the most abundant chemical substance in the universe, constituting roughly 75% of all normal matter.However, most of the universe's mass is not in the form of baryons or chemical elements. See dark matter and dark energy. Stars such as the Sun are mainly composed of hydrogen in the plasma state. Most of the hydrogen on Earth exists in molecular forms such as water and organic compounds. For the most common isotope of hydrogen (symbol 1H) each atom has one proton, one electron, and no neutrons. In the early universe, the formation of protons, the nuclei of hydrogen, occurred during the first second after the Big Bang. The emergence of neutral hydrogen atoms throughout the universe occurred about 370,000 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
