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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 ...
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 ...
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 ]
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to electrons making a transition from a high energy state to a lower energy state. The photon energy of the emitted photons is equal to the energy difference between the two states. There are many possible ...
The decay scheme of a radioactive substance is a graphical presentation of all the transitions occurring in a decay, and of their relationships. Examples are shown below. It is useful to think of the decay scheme as placed in a coordinate system, where the vertical axis is energy, increasing from bottom to top, and the horizontal axis is the proton number, increasing from left to right.
The rate of spontaneous emission (i.e., the radiative rate) can be described by Fermi's golden rule. [17] The rate of emission depends on two factors: an 'atomic part', which describes the internal structure of the light source and a 'field part', which describes the density of electromagnetic modes of the environment.
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.
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 ...