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  2. Stimulated emission - Wikipedia

    en.wikipedia.org/wiki/Stimulated_emission

    This process is known as stimulated emission. In a group of such atoms, if the number of atoms in the excited state is given by N 2, the rate at which stimulated emission occurs is given by = = where the proportionality constant B 21 is known as the Einstein B coefficient for that particular transition, and ρ(ν) is the radiation density of ...

  3. Einstein coefficients - Wikipedia

    en.wikipedia.org/wiki/Einstein_coefficients

    Schematic diagram of atomic stimulated emission. Stimulated emission (also known as induced emission) is the process by which an electron is induced to jump from a higher energy level to a lower one by the presence of electromagnetic radiation at (or near) the frequency of the transition. From the thermodynamic viewpoint, this process must be ...

  4. Lewis antigen system - Wikipedia

    en.wikipedia.org/wiki/Lewis_antigen_system

    There are two main types of Lewis antigens, Lewis a (Le-a) and Lewis b (Le-b). There are three common phenotypes: Le(a+b-), Le(a-b+), and Le(a-b-). [2] The enzyme fucosyltransferase 3 (FUT3), encoded by Le gene, adds a fucose to the precursor oligosaccharide substrate, converting it to the Le-a antigen. People who have the Le allele and who are ...

  5. STED microscopy - Wikipedia

    en.wikipedia.org/wiki/STED_microscopy

    Stimulated emission depletion (STED) microscopy is one of the techniques that make up super-resolution microscopy. It creates super-resolution images by the selective deactivation of fluorophores , minimizing the area of illumination at the focal point, and thus enhancing the achievable resolution for a given system. [ 1 ]

  6. Population inversion - Wikipedia

    en.wikipedia.org/wiki/Population_inversion

    The energy released in this transition may be emitted as a photon (spontaneous emission), however in practice the 3 → 2 transition called the Auger effect (labeled R in the diagram) is usually radiationless, with the energy being transferred to vibrational motion of the host material surrounding the atoms, without the generation of a photon.

  7. Active laser medium - Wikipedia

    en.wikipedia.org/wiki/Active_laser_medium

    The simplest model of optical gain in real systems includes just two, energetically well separated, groups of sub-levels. Within each sub-level group, fast transitions ensure that thermal equilibrium is reached quickly. Stimulated emissions between upper and lower groups, essential for gain, require the upper levels to be more populated than ...

  8. Blood type - Wikipedia

    en.wikipedia.org/wiki/Blood_type

    A complete blood type would describe each of the 45 blood groups, and an individual's blood type is one of many possible combinations of blood-group antigens. [3] Almost always, an individual has the same blood group for life, but very rarely an individual's blood type changes through addition or suppression of an antigen in infection, malignancy, or autoimmune disease.

  9. Solar radio emission - Wikipedia

    en.wikipedia.org/wiki/Solar_radio_emission

    Maser is an acronym for "microwave amplification by stimulated emission of radiation", which originally referred to a laboratory device that can produce intense radiation of a specific frequency through stimulated emission. Stimulated emission is a process by which a group of atoms are moved into higher energy levels (above thermal equilibrium ...