Spectral density emission

This is known as the Planck radiation law. Figure A2.2.3 shows this spectral density fiinction. The surface temperature of a hot body such as a star can be estimated by approximating it by a black body and measuring the frequency at which the maximum emission of radiant energy occurs. It can be shown that the maximum of the Planck spectral density occurs at 2.82. So a measurement of yields an estimate of the... 

For most treatments, the spectral density, J(a>), Eq. 2.86, also referred to as the spectral profile or line shape, is considered, since it is more directly related to physical quantities than the absorption coefficient a. The latter contains frequency-dependent factors that account for stimulated emission. For absorption, the transition frequencies ojp are positive. The spectral density may also be defined for negative frequencies which correspond to emission. 

We note that the collision-induced emission profile may be obtained from the spectral density, J(co), according to... 

Emission and absorption spectra are thus given by the same basic profile, J(co), commonly referred to as the spectral density, times some factors that depend on frequency. The exponential in Eq. 5.2 accounts for stimulated emission (see pp. 48ff.). The factor co of Eq. 5.2 is typical for absorption, just as the factor co3 is typical for the emission probability, Eq. 5.4, see also pp. 49ff. 

The hemispherical emissive power E is defined as the radiant flux density (W/m2) associated with emission from an element of surface area dA into a surrounding unit hemisphere whose base is copla-nar with dA. If the monochromatic intensity ( 2, X) of emission from the surface is isotropic (independent of the angle of emission, 2), Eq. (5-101) may be integrated over the 2k sr of the surrounding unit hemisphere to yield the simple relation Ex = nix, where >, = Ex(X) is defined as the monochromatic or spectral hemispherical emissive power. 

The extinction coefficient and emission rate are defined through the spectral density function G (v) that combines the effects of solvent-induced inhomogeneous broadening and vibrational excitations of the donor-acceptor complex. A substantial simplification of the description can be achieved if the two types of nuclear motions are not coupled to each other. The spectral density G (v) is then given by the convolution ... 

The total spectral density of quasi-equilibrium plasma emission in continuous spectrum consists of the bremsstrahlung and recombination components, which can be combined in one general expression ... 

We can observe that in this case, the cell measured noise emission spectral density is not flat versus frequency. Therefore we may consider that is composed of two components a constant noise spectral density due to the electrolyte itself an excess noise spectral density... 

An analysis of RTS in this work quantitatively explains details of hole trapping processes in the tetrahedral-shaped recess quantum dot structure. Noise spectral density is given by superposition of 1/f noise and RTS pulses (Fig. 16) with the activation energy AEke= 190 meV for hole emission and AE),c= 260 meV for hole capture. RTS noise ampUtude has its maximum value at temperature range below 300 K when the quasi Fermi level coincides with the trap energy level. At temperature higher than 300 K the 1/f noise component is dominant and then parameter Cq given by (4) is used as quality and rehabihty indicator. 

The forward spectrum of sodium at density of 1.8 10 cm irradiated by laser with frequency loi to the blue of the D2 transition is shown in figure 1. This spectrum contains, in addition to the laser radiation, a spectrally broad off-axis conical emission attributed by us to a Cherenkov-type emission, and a narrow coherent peak to the blue of the Di transition - the "blue peak". This spectrally narrow emission is on-axis and has a threshold on the laser intensity. Thus, this emission is a stimulated one. Within the resolution of our spectrometer, its frequency does not depend on the laser detuning from the D2 transition. 

In this equation, the Franck-Condon factors (the squared Franck-Condmi integrals) and the resonance condition [the delta function in Eq. (4)] have been absorbed into the spectral density 2>eet [135]. It can be factored into the line-shape functions for donor emission and acceptor absorption (this is only possible due to the assumption of local vibrational modes). In addition, the dipole approximation can be made for the electronic coupling matrix element ... 

This table summarizes some characteristics and the expected performance of IRAS. The noise equivalent flux density and noise equivalent spectral density have been computed on the basis of a zodiacal emission of 3 x 10 W cm sr and a telescope temperature of 16K, while the orbital scan rate... 

QD distribution owing to the lower spectral density of QD emission. However, no sharp lines could be isolated on the low energy side of the QD emission spectrum, for reasons that are so far not clear. We first checked that the intensity of these lines varies linearly with exciting power, in the low power regime this shows that the observed sharp lines correspond to the recombination of a single electron-hole pair and not to excited states recombination. 

W/(m ster). This is about 50 times larger than the radiance of the sun. For the spectral density of the radiance the comparison is even more dramatic. Since the emission of an unstabilized single-mode laser is restricted to a spectral range of about 1 MHz, the laser has a spectral... 

The maximum of spectral density of the sun s radiation emission corresponds to the wavelength k = 500 nm. Assuming that the sun radiates like an IBB, determine ... 

The integral of the temperature gradient of the spectral power density from wavelength Xl to X2, is readily calculable using the Planck radiation law (5). Constant emissivity is assumed for equation 3. 

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