These are organized by a classification scheme developed exclusively for Cosma. More…
molecule : the smallest particle of a substance that retains all the properties of the substance and is composed of one or more atoms — Webster
Molecule is an electrically neutral group of two or more atoms held together by chemical bonds. A molecule may be homonuclear, that is, it consists of atoms of one chemical element, as with oxygen (O2); or it may be heteronuclear, a chemical compound composed of more than one element, as with water (H2O). Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are generally not considered single molecules.
Molecules as components of matter are common in organic substances (and therefore biochemistry). They also make up most of the oceans and atmosphere. However, the majority of familiar solid substances on Earth, including most of the minerals that make up the crust, mantle, and core of the Earth, contain many chemical bonds, but are not made of identifiable molecules. Also, no typical molecule can be defined for ionic crystals (salts) and covalent crystals (network solids), although these are often composed of repeating unit cells that extend either in a plane (such as in graphene) or three-dimensionally (such as in diamond, quartz, or sodium chloride). The theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding, which means that solid metals are also not made of molecules. In glasses (solids that exist in a vitreous disordered state), atoms may also be held together by chemical bonds with no presence of any definable molecule, nor any of the regularity of repeating units that characterizes crystals. — Wikipedia
Molecular physics is the study of the physical properties of molecules, the chemical bonds between atoms as well as the molecular dynamics. Its most important experimental techniques are the various types of spectroscopy; scattering is also used. The field is closely related to atomic physics and overlaps greatly with theoretical chemistry, physical chemistry and chemical physics.
In addition to the electronic excitation states which are known from atoms, molecules exhibit rotational and vibrational modes whose energy levels are quantized. The smallest energy differences exist between different rotational states: pure rotational spectra are in the far infrared region (about 30 – 150 µm wavelength) of the electromagnetic spectrum. Vibrational spectra are in the near infrared (about 1 – 5 µm) and spectra resulting from electronic transitions are mostly in the visible and ultraviolet regions. From measuring rotational and vibrational spectra properties of molecules like the distance between the nuclei can be specifically calculated.
One important aspect of molecular physics is that the essential atomic orbital theory in the field of atomic physics expands to the molecular orbital theory. — Wikipedia
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Extending nucleic acid memory (NAM)
on May 29, 2020 at 11:40 am
Humanity is creating huge amounts of data every day, billions of emails and social media updates, new websites, documents, images, and scientific and commercial big data amounting to petabytes of storage needs and beyond. It is well recognised that nucleic acids, the RNA and DNA that encode the proteins needed to build living things are seemingly quite efficient in storing information and so taking inspiration from this realm, a team from India writes in the International Journal of Nano and […]
A new horizon for vibrational circular dichroism...
on May 29, 2020 at 11:37 am
Vibrational circular dichroism (VCD) spectroscopy is an extension of circular dichroism spectroscopy into the infrared and near-infrared regions where vibrational transitions occur in the ground electronic state of a molecule. The method offers the advantage of studying the chiroptical properties of a wide range of molecules in non-crystalline states.
NASA's AIM spots first Arctic noctilucent clouds...
on May 29, 2020 at 11:36 am
Ice-blue clouds are drifting high above the Arctic, which means the Northern Hemisphere's noctilucent cloud season is here.
Researchers track how bacteria purge toxic metals
on May 29, 2020 at 7:40 am
Bacteria have a cunning ability to survive in unfriendly environments.
Two bacteria allow spittlebugs to thrive on...
on May 29, 2020 at 7:39 am
A new study examines the symbiotic relationship between two types of bacteria and spittlebugs that helps the insect live on very low-nutrient food. The bacteria use a metabolic "trick" also employed by cancer cells to create the right conditions for converting the poor food into the necessary building blocks for survival.