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Topic: Atomic units


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  Definitions of the SI units: Non-SI units
Units outside the SI Certain units are not part of the International System of Units, that is, they are outside the SI, but are important and widely used.
The unified atomic mass unit is equal to 1/12 of the mass of an unbound atom of the nuclide
The astronomical unit is a unit of length.
physics.nist.gov /cuu/Units/outside.html   (466 words)

  
  tScholars.com | Atomic units   (Site not responding. Last check: )
Atomic units (au) form a system of units convenient for atomic physics, electromagnetism, and quantum electrodynamics, especially when the focus is on the properties of electrons.
Both Planck units and au are derived from certain fundamental properties of the physical world, and are free of anthropocentric considerations.
Beyond this, Planck units normalize to 1 the two fundamental constants of general relativity and cosmology: the gravitational constant G and the speed of light in a vacuum, c.
www.tscholars.com /encyclopedia/Atomic_units   (555 words)

  
 Spartanburg SC | GoUpstate.com | Spartanburg Herald-Journal
Atomic units (au) form a system of units convenient for atomic physics, electromagnetism, and quantum electrodynamics, especially when the focus is on the properties of electrons.
Both Planck units and au are derived from certain fundamental properties of the physical world, and are free of anthropocentric considerations.
Beyond this, Planck units normalize to 1 the two fundamental constants of general relativity and cosmology: the gravitational constant G and the speed of light in a vacuum, c.
www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=atomic_units   (506 words)

  
 The Structure of the Physical Universe, Chapter XXXI
Since each unit of rotational displacement is equal to two units of atomic mass the effect of this process is to increase or decrease the rotational mass by 2n units.
One unit of electric time displacement is required for each rotational displacement unit, the equivalent of two units of atomic mass.
The atomic transformations which have been discussed thus far are primarily exchange reactions, in which some of the motion of one of the participants is transferred to the other, or fragmentation reactions, in which one or both of the participants are broken up into smaller units.
www.reciprocalsystem.com /spu/spu31.htm   (4203 words)

  
 Units: K
The unit is often abbreviated K, although this conflicts with the symbol for the kelvin.
a metric unit of magnetic flux density equal to 1000 gauss or 0.1 tesla.
One kilogram mole of a compound is the number of kilograms of the compound equal to the molecular weight of a molecule of that compound measured in atomic mass units.
www.unc.edu /~rowlett/units/dictK.html   (3827 words)

  
 Atomic Units
Atomic units are convenient units to describe the properties of electrons.
The atomic units have been chosen such that the fundamental electron properties are all equal to one atomic unit.
In atomic units the mass of a proton (1.6726 x 10-27 kg) would be 1836.15 au, and the reduced mass of the hydrogen molecule (.503913 g/mol) would be 925.260 au.
cat.middlebury.edu /~chem/chemistry/class/physical/quantum/help/atomic/atomic.html   (108 words)

  
 NIST: Atomic Spectroscopy - Introduction
Atomic radiation is discussed, in particular the wavelengths, intensities, and shapes of spectral lines, and a few remarks are made regarding continuous spectra.
In addition to frequency and wavenumber units, atomic energies are often expressed in electron volts (eV).
The unit of energy in the system of atomic units (a.u.) often used for theoretical calculations is the hartree, which is equal to 2 rydbergs.
physics.nist.gov /Pubs/AtSpec/node01.html   (401 words)

  
 Offer to sell
The absorbance of a solution per unit of path length and per unit concentration; a = A/(bc) where a, A, b, and c are the absorptivity, absorbance, path length, and concentration, respectively.
The definitions of atomic units include physical constants (like the speed of light, the rest mass of the electron, and other quantities that never change), so that all constants drop out of expressions when atomic units are used.
The atomic weight given on the periodic table is a weighted average of isotopic masses found in a typical terrestrial sample of the element.
www.hantra.com /data/dictionary.php?pd=A   (3707 words)

  
 Chemistry: WebElements Periodic Table : Periodic properties : Standard atomic weights (IUPAC 1997): Definition
"An atomic weight (relative atomic mass) of an element from a specified source is the ratio of the average mass per atom of the element to 1/12 of the mass of
An entry in [square brackets] indicates the mass number of the longest-lived isotope of an element that has no stable isotopes and for which a standard atomic weight cannot be defined because of wide variability in isotopic composition (or complete absence) in nature.
The difference between the atomic weight of the element in such specimens and that given in the table may exceed the stated uncertainty.
www.webelements.com /webelements/properties/text/definitions/atomic-weight.html   (678 words)

  
 BIPM - accepted for use
The two most important of such unit systems based on fundamental constants are the natural unit (n.u.) system used in high energy or particle physics, and the atomic unit (a.u.) system used in atomic physics and quantum chemistry.
Although the use of SI units is to be preferred for reasons already emphasized, authors who see a particular advantage in using these non-SI units should have the freedom to use the units that they consider to be best suited to their purpose.
Since, however, SI units are the international meeting ground in terms of which all other units are defined, those who use units from Tables 8 and 9 should always give the definition of the units they use in terms of SI units.
www.bipm.org /en/si/si_brochure/chapter4/4-1.html   (1367 words)

  
 Periodic Table : Periodic properties : Standard atomic weights (IUPAC 1997): Definition
The atomic weight is the average of the isotope weights weighted for the isotope distribution and expressed on the
The table below of atomic weights is adapted from the 1997 report of the IUPAC Atomic Weights and Isotopic Abundances Commission entitled "Atomic Weights of the Elements 1997" (ref 3).
The standard atomic weights apply to the elements as they exist naturally on Earth, and the uncertainties take into account the isotopic variation found in most laboratory samples.
www.webelements.com /webelements/scholar/properties/definitions/atomic-weight.html   (678 words)

  
 Atomic units, universal constants, conversion factors
The choice of fundamental constants defining these units is given in Table 9.1, which includes also the ``Kelvin'', ``mole'' and ``radian'', not fundamental constants and not exactly associated with atomic units in common practice, but which are not expressible in terms of the four fundamental constants
A list of the values in atomic units for some universal constants is given in Table 9.2.
A list of the conversion factors from the SI and cgs systems to atomic units is given in Table 9.3.
folk.uio.no /michalj/node10.html   (121 words)

  
 APS Units
Units aid the Society in fulfilling its mission to “advance and diffuse the knowledge of physics.”
As part of a Society committed to member participation, the units provide opportunities for members to interact with colleagues with similar interests and to keep abreast of new developments in their specialized fields.
Furthermore, most units communicate with their members on a regular basis, supplying timely information on upcoming events as well as reports on new developments in their areas of interest.
www.aps.org /membership/units   (175 words)

  
 Atomic units
In atomic and molecular physics, it is convenient to use the elementary charge, e, as the unit of charge, and the electron mass,
A fuller list of atomic units and their precise values is PQRG, page 51.
Another energy unit in common use is the electron- volt, which is the energy acquired by an electron falling through the potential difference of 1 volt: it has its origin in experimental practice and can also be viewed as a mixed atomic-SI unit.
galileo.phys.virginia.edu /classes/311/notes/units/node2.html   (381 words)

  
 gram-atomic weight - Encyclopedia.com
gram-atomic weight amount of an atomic substance whose weight, in grams, is numerically equal to the atomic weight of that substance.
For example, 1 gram-atomic weight of atomic oxygen, O (atomic weight approximately 16), is 16 grams.
For permission to reuse this article, contact Copyright Clearance Center.
www.encyclopedia.com /doc.aspx?id=1E1:gramatom   (71 words)

  
 Atomic units - Definition, explanation
Atomic units(au) are a convenient system of units of measurement used in atomic physics, particularly for describing the properties of electrons.
The use of atomic units also simplifies the Schrödinger equation.
For example the Hamiltonian for an electron in the hydrogen atom would be:
www.calsky.com /lexikon/en/txt/a/at/atomic_units.php   (122 words)

  
 Atomic Mass Units
It's much more convenient to use something called the atomic mass unit, or amu.
Many versions of the periodic table (though not ours) give the atomic masses of the elements in amu; these are average masses, taking into account the different
He used the hydrogen atom as a unit--one oxygen atom has a mass of sixteen hydrogens, and so forth.
www.colorado.edu /physics/2000/periodic_table/atomic_mass.html   (213 words)

  
 Dictionary of Technical Terms for Aerospace Use - A
Although it was already obvious on the occasion of the 8th CGPM (1933) that there was a unanimous desire to replace those "international" units by so-called "absolute" units, the official decision to abolish them was only taken by the 9th CGPM (1948), which adopted for the unit of electric current, the ampere," which see.
The alpha particle has an atomic weight of 4 and a positive charge equal in magnitude to 2 electronic charges; hence it is essentially a helium nucleus (helium atom stripped of its two planetary electrons).
In astronomical units, the mean distance of the earth from the sun, calculated by the Kepler law from the observed mean motion n and adopted mass m, is 1.00000003.
tcp-impl.grc.nasa.gov /~dglover/dictionary/a.html   (13387 words)

  
 atomic mass unit
Since 1961, by definition the unified atomic mass unit is equal to one-twelfth of the mass of the nucleus of a carbon-12 atom.
Although not an SI unit, the unified atomic mass unit is accepted by the CGPM for use with SI.
physicists were using an atomic mass unit defined as equal to one-sixteenth of the mass of the oxygen-16 atom (the isotope of oxygen containing a total of 16 protons and neutrons).
www.sizes.com /units/atomic_mass_unit.htm   (1093 words)

  
 DENSITY COMPARISON RIDDLE   (Site not responding. Last check: )
Using a weighted average the average atomic weight of air is (0.78*28.02 + 0.21*32 + 0.01*39.94 = 28.97 atomic units.
If the air is 2% water vapor then the air is 98% air with an atomic weight of 28.97 and 2% water vapor in which the water vapor has 18 atomic units.
Using a weighted average the average atomic weight of the air with 2% water vapor is (0.98*28.97 + 0.02*18 = 28.75 atomic units.
www.theweatherprediction.com /habyhints2/482   (263 words)

  
 Atomic Theory
Atomic weight is the weight of an atom expressed in atomic mass units (amu).
Scientists determine the atomic weight of an element with more than one isotope by averaging the weights of all the isotopes in the proportions in which they occur in nature.
This value is an average for the two isotopes chlorine 35 (atomic weight 34.96885) and chlorine 37 (atomic weight 36.96590) in their natural proportions.
www.laughtergenealogy.com /bin/histprof/misc/atomic.html   (3920 words)

  
 Polarizability and Hyperpolarizability Calculation   (Site not responding. Last check: )
Polarizability (alpha): Cubic atomic units and cubic Angstroms.
Dimensional analysis of the quadratic hyperpolarizability indicates that is possesses the units of dipole moment
Sometimes these units are simply referred to as esu.
www.cachesoftware.com /mopac/Mopac2002manual/node629.html   (172 words)

  
 Introductory Terms, Page 2
one atomic mass unit is equal to 1/12th the mass of one atom of Carbon-12.
Atomic weight is the decimal number most commonly associated with each element's symbol on the Periodic Chart.
The values for the atomic weights of the elements are calculated by summing the products of the different individual Isotope Masses multiplied by the decimal equivalent of their percent of abundance values.
www.bcpl.net /~kdrews/introterms/intro2.html   (823 words)

  
 The Nature of the Problem - Units of Measurement used in Atomic Physics   (Site not responding. Last check: )
The regular cgs system of units is inconvenient to use on the atomic level as the sizes of the standard units in this system are too large.
Instead, a system of units called atomic units, based on atomic values for energy, length, etc., is employed.
Atomic units are defined in terms of Planck's constant and the mass and charge of the electron:
www.chemistry.mcmaster.ca /esam/Chapter_1/section_2.html   (324 words)

  
 Nuclear Units
Nuclear masses are measured in terms of atomic mass units with the carbon-12 nucleus defined as having a mass of exactly 12 amu.
The number of protons is called the atomic number and determines the chemical element.
Nuclei of a given element (same atomic number) may have different numbers of neutrons and are then said to be different isotopes of the element.
hyperphysics.phy-astr.gsu.edu /hbase/nuclear/nucuni.html   (416 words)

  
 Atomic Mass Units   (Site not responding. Last check: )
Another way is to define a new mass unit and say that it is equal to the mass of one hydrogen atom.
That unit is called the atomic mass unit (amu) and is defined, for the moment, as the mass of one hydrogen atom.
Using the current standard, the actual definition of an atomic mass unit is that it is 1/12th of the mass of one atom of the carbon-12 isotope.
dl.clackamas.cc.or.us /ch104-03/atomic1.htm   (244 words)

  
 Atomic Motion - Case Studies
With 15 properties and over 4,500 units in Ottawa, Paramount Properties has been at the forefront of the apartment rental industry for over 20 years, offering an extraordinary standard of living to tenants.
Atomic Motion helped to re-define the website's primary goals: improve the site navigation, design a compelling interface, significantly increase quality visits, increase the exposure of the apartment units and raise the profile of the company.
Atomic Motion’s redesign of the information architecture resulted in stronger brand presence and identity.
www.atomicmotion.com /clients/studies.aspx   (457 words)

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