|
Water Window
The water window is a region of the electromagnetic spectrum in which water is transparent to soft x-rays. The window extends from the K-absorption edge of carbon at 282 eV (68 PHz, 4.40 nm wavelength) to the K-edge of oxygen at 533 eV (129 PHz, 2.33 nm wavelength). Water is transparent to these X-rays, but carbon (and thus, organic molecules) is absorbing. These wavelengths could be used in an x-ray microscope An X-ray microscope uses electromagnetic radiation in the soft X-ray band to produce magnified images of objects. Since X-rays penetrate most objects, there is no need to specially prepare them for X-ray microscopy observations. Unlike visible li ... for viewing living specimens. References * {{X-ray science X-rays ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnetic Spectrum
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 1025 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus. This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications. There is no known limit for long and short wavelengths. Extreme ultr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent). It is vital for all known forms of life, despite not providing food, energy or organic micronutrients. Its chemical formula, H2O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°. "Water" is also the name of the liquid state of H2O at standard temperature and pressure. A number of natural states of water exist. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds consist of suspended droplets of water and ice, its solid state. When finely divided, crystalline ice may precipitate in the form of snow. The gaseous state of water is steam or water vapor. Water co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soft X-ray
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] |
Absorption Edge
An absorption edge, absorption discontinuity or absorption limit is a sharp discontinuity in the absorption spectrum of a substance. These discontinuities occur at wavelengths where the energy of an absorbed photon corresponds to an electronic transition or ionization potential. When the quantum energy of the incident radiation becomes smaller than the work required to eject an electron from one or other quantum states in the constituent absorbing atom, the incident radiation ceases to be absorbed by that state. For example, incident radiation on an atom of a wavelength that has a corresponding energy just below the binding energy of the K-shell electron in that atom cannot eject the K-shell electron."The Penguin Dictionary of Physics", 3rd ed., Longman Group Ltd. (2000), p. 3. Siegbahn notation is used for notating absorption edges. In compound semiconductors, the bonding between atoms of different species forms a set of dipoles. These dipoles can absorb energy from an electromag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
K-edge
In X-ray absorption spectroscopy, the K-edge is a sudden increase in x-ray absorption occurring when the energy of the X-rays is just above the binding energy of the innermost electron shell of the atoms interacting with the photons. The term is based on X-ray notation, where the innermost electron shell is known as the K-shell. Physically, this sudden increase in attenuation is caused by the photoelectric absorption of the photons. For this interaction to occur, the photons must have more energy than the binding energy of the K-shell electrons (K-edge). A photon having an energy just above the binding energy of the electron is therefore more likely to be absorbed than a photon having an energy just below this binding energy or significantly above it. The energies near the K-edge are also objects of study, and provide other information. Use The two radiocontrast agents iodine and barium have ideal K-shell binding energies for absorption of X-rays: 33.2 keV and 37.4 keV ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Molecule
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The study of the properties, reactions, and syntheses of organic compounds comprise the discipline known as organic chemistry. For historical reasons, a few classes of carbon-containing compounds (e.g., carbonate salts and cyanide salts), along with a few other exceptions (e.g., carbon dioxide, hydrogen cyanide), are not classified as organic compounds and are considered inorganic. Other than those just named, little consensus exists among chemists on precisely which carbon-containing compounds are excluded, making any rigorous definition of an organic compound elusive. Although organic compounds make up only a small percentage of Earth's crust, they are of central importance because all known life is based on organic compounds. Living thin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray Microscope
An X-ray microscope uses electromagnetic radiation in the soft X-ray band to produce magnified images of objects. Since X-rays penetrate most objects, there is no need to specially prepare them for X-ray microscopy observations. Unlike visible light, X-rays do not reflect or refract easily and are invisible to the human eye. Therefore, an X-ray microscope exposes film or uses a charge-coupled device (CCD) detector to detect X-rays that pass through the specimen. It is a contrast imaging technology using the difference in absorption of soft X-rays in the water window region (wavelengths: 2.34–4.4 nm, energies: 280–530 eV) by the carbon atom (main element composing the living cell) and the oxygen atom (an element of water). Microfocus X-ray also achieves high magnification by projection. A microfocus X-ray tube produces X-rays from an extremely small focal spot (5 μm down to 0.1 μm). The X-rays are in the more conventional X-ray range (20 to 300 keV) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.svg "Click for more on -> Water")
