Search results
Results from the WOW.Com Content Network
Next, suppose we have a material that violates Kirchhoff's law when integrated, such that the total coefficient of absorption is not equal to the coefficient of emission at a certain , then if the material at temperature is placed into a Hohlraum at temperature , it would spontaneously emit more than it absorbs, or conversely, thus ...
In spectroscopy, oscillator strength is a dimensionless quantity that expresses the probability of absorption or emission of electromagnetic radiation in transitions between energy levels of an atom or molecule. [1] [2] For example, if an emissive state has a small oscillator strength, nonradiative decay will outpace radiative decay.
An overview of absorption of electromagnetic radiation.This example shows the general principle using visible light as a specific example. A white light source—emitting light of multiple wavelengths—is focused on a sample (the pairs of complementary colors are indicated by the yellow dotted lines).
In atomic, molecular, and optical physics, the Einstein coefficients are quantities describing the probability of absorption or emission of a photon by an atom or molecule. [1] The Einstein A coefficients are related to the rate of spontaneous emission of light, and the Einstein B coefficients are related to the absorption and stimulated ...
An emission spectrum is formed when an excited gas is viewed directly through a spectroscope. Schematic diagram of spontaneous emission. Emission spectroscopy is a spectroscopic technique which examines the wavelengths of photons emitted by atoms or molecules during their transition from an excited state to a lower energy state.
The oscillator strength for any transition between ground and excited state depends on these coefficients. The absorption cross-section (σ λ) is empirically determined from this oscillator strength and the broadening of the absorption/emission line by collisions, the Doppler effect and the uncertainty principle.
Solutions to the equation of radiative transfer form an enormous body of work. The differences however, are essentially due to the various forms for the emission and absorption coefficients. If scattering is ignored, then a general steady state solution in terms of the emission and absorption coefficients may be written:
Chemical interactions in contrast change the polarizability and thus absorption. In solids, attenuation is usually an addition of absorption coefficient α {\displaystyle \alpha } (creation of electron-hole pairs) or scattering (for example Rayleigh scattering if the scattering centers are much smaller than the incident wavelength). [ 17 ]