Wings, spectral

According to the uncertainty principle the non-exponential short-time behaviour of Kt determines the deviation of the high-frequency spectral wings from Lorentzian shape. The actual spectrum obtained by substitution of Eq. (2.53) into Eq. (2.13) is bi-Lorentzian ... 

Using the impact approximation presented in Chapter 6, they may easily be found for any rotational band even if rotational-vibrational interaction is nonlinear in J. In 1954 R W. Anderson proved as a theorem [104] that expansion of the spectral wings in inverse powers of frequency is controlled by successive odd derivatives of the correlation function at the origin. In impact approximation the lowest non-zero derivative of this type is the third and therefore asymptotics G/(co) is described by the power expansion [20]... 

Rachet F, Chrysos M, Guillot NC, Le Duff Y (2000) Unique case of highly polarized collision-induced light scattering The very far spectral wing by the helium pair. Phys Rev Lett 84 2120-2123... 

For the vibration of CF4, the Raman polarizability tensor of an isolated molecule is isotropic, and, consequently, monomer polarizabilities of Eq. (2) do not contribute to Vj depolarized Raman spectral wings. On the other hand, the Raman incremental pair polarizability tensor for the normal vibration V that takes place in Eq. (2) is [78]... 

In Fig. 4d, the effect of spin dilution is illustrated. Spectral broadening is clearly evident in the spectral wings of the fully labeled sample. The shortest distance between two adjacent monomers based on the X-ray structure (PDB 18L8) can now be simulated with the software MMM (http //www.epr.ethz.ch/software/index) based on a rotamer library approach [7] showing a mean distance of 1.4 nm, in agreement with the dipolar broadening observed. 

A second assumption of this method concerns the shape of the collision Induced spectrum, which, as suggested by the spectral wings, is taken to be essentially exponential ... 

The treatment given so far takes account of neither the effects of local electrical fields [11-13] on the spectral intensity or dynamics nor the contribution to the spectra of interaction-induced intensity [14-16]. The first effect, caused by the fact that (due to interactions) the molecules in the fluid do not see the same electric field as that propogated into the medium, is partially eliminated [6] by normalisation of C(t) -eqns. 2.4 to 2.6. The second effect, which usually distorts the spectral wings (at high frequencies) is largely unknown for most liquids and certainly affects [16,17] the short time part of C(t). 

When a uniaxial elongation or compression is applied to the network, the resonance spectrum suffers large alterations. A well resolved doublet appears, together with spectral wings expanding on both sides of the spectrum (fig b). 

One effect of saturation, and the dependence of e on /, is to decrease the maximum absorption intensity of a spectral line. The central part of the line is flattened and the intensity of the wings is increased. The result is that the line is broadened, and the effect is known as power, or saturation, broadening. Typically, microwave power of the order of 1 mW cm may produce such broadening. Minimizing the power of the source and reducing the absorption path length t can limit the effects of power broadening. 

R. K. Winge, V A. Fassel, V. J. Peterson, and M. A. Floyd. Inductively Coupled Plasma Atomic Emission Spectroscopy An Atlas of Spectral Information. Elsevier, Amsrerdam, 1985. ICP-OES specrral scans near emission lines usefol for analysis. 

Experimental verification of the universal wing shape (4.90) is not only an important way of checking the dominant role of spectral exchange but also an additional spectroscopic way to measure energy relaxation time even before collapse (in rare gases). Unfortunately it has not been done yet due to lack of accuracy far beyond the spectral edge. 

Let us note that sometimes spectra are so well resolved that even some asymmetry of lines is registered [283]. This means that the wings of individual components of a spectral band become observable. Hence, non-adiabatic secularization becomes too crude an approximation. The experiment [283] was interpreted by Kouzov [280] taking into account the co-dependent diagonal part of the relaxational operator. 

We see that as spectral width is increased, the spectra have to be shifted to longer wavelengths to maintain the proper X/Y ratio, otherwise the short wavelength wing would yield an orange color shift. This has the disastrous consequence, however, of drastically reducing the values of X and Y, since the broadened, shifted spectra make increasingly poorer matches to the x and y curves. 

Thus, spectral interferences in atomic spectroscopy are less likely than in molecular spectroscopy analysis. In any case, even the atomic lines are not completely monochromatic i.e. only one wavelength per transition). In fact, there are several phenomena which also bring about a certain broadening . Therefore, any atomic line shows a profile (distribution of intensities) as a function of wavelength (or frequency). The analytical selectivity is conditioned by the overall broadening of the lines (particularly the form of the wings of such atomic lines). 

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