Bandwidth, spectral

Low and High frequency can be restored by use of a deconvolution algorithm that enhances the resolution. We operate an improvement of the spectral bandwidth by Papoulis deconvolution based essentially on a non-linear adaptive extrapolation of the Fourier domain. 

Spectral bandwidth of emis- Statistical weight of atomic g... 

Spectral bandwidth of excita- Stefan-Boltzmann constant a... 

Several factors affect the bandshapes observed ia drifts of bulk materials, and hence the magnitude of the diffuse reflectance response. Particle size is extremely important, siace as particle size decreases, spectral bandwidths generally decrease. Therefore, it is desirable to uniformly grind the samples to particle sizes of <50 fim. Sample homogeneity is also important as is the need for dilute concentrations ia the aoaabsorbiag matrix. 

Fig. 4. Sensitivity for the detection of CO using spectral thermography as a function of absorbing path length. Detector NEP = 30 pW, J = 1.0 mW/cm, A = 1.5E — 5 cm, samples = 60, number of detectors = 600, G = 6.6E5 ppm-cm center wavelength = 4.65 /im spectral bandwidth = 0.2 fim.

It should be noted that when we compare the brightness of a LGS to a NGS, the result depends on the spectral bandwidth, because the LGS is a line source, whereas the NGS is a continuum one. The magnitude scale is a logarithmic measure of flux per spectral interval (see Ch. 15). This means that a (flat) continuum source has a fixed magnitude, no matter how wide the filter is. In contrast, the magnitude of a line source is smaller for narrower bandpasses. It is therefore advisable to use the equivalent magnitude only for qualitative arguments. The photon flux should be used in careful system analyses. 

In the hrst case, the degree of self coherence depends on the spectral characteristics of the source. The coherence time Tc represents the time scale over which a held remains correlated this hme is inversely proportional to the spectral bandwidth Au) of the detected light. A more quantitative dehnition of quasi-monochromatic conditions is based on the coherence time all relevant delays within the interferometer should be much shorter than the coherence length CTc. A practical way to measure temporal coherence is to use a Michel-son interferometer. As we shall see, in the second case the spatial coherence depends on the apparent extent of a source. 

A delay error shifts the position of zero delay with respect to the overall intensity envelope, resulting in a substantial reduction of overall contrast. The contrast may vanish entirely if the zero delay position coincides with a minimum. Therefore, there is a relation between the allowable delay error max and the spectral bandwidth Aoj of the detected radiation if the amplitude error of the fringe modulation is to remain small, i. e., (5max = A /AA. 

Stewart, J. E., Spectral-bandwidth effects of variable-wavelength absorption detectors in liquid chromatography, ]. Chromatogr., 174, 283, 1979. 

It should be noted that no geometrical relaxation of the excited state geometry was considered in our calculations. Such relaxations may well occur to some degree and would then enhance the localization of the electronic excitation. However the relatively narrow spectral bandwidth suggests that the geometrical changes associated with excitation into the first excited singlet state are only minor. 

Consider the dynamics of ionization of clusters through the C state of an ammonia molecule, where it should be noted that it is also possible that the excitation leads to some population of the B states due to the broad spectral bandwidth of the femtosecond laser pulses. The measurements indicate lifetimes... 

Considering the spectral bandwidth of the light sources, they can be classified into three main groups ... 

A typical spectral bandwidth of LED is within the range of 20-50 nm (it varies from type to type and is the lowest for superluminescent diodes - 5 nm). LEDs cover the whole visible range starting from 370 nm up to infra red radiation. The radiation emitted by an LED depends on the... 

Site-selection spectroscopy Maximum selectivity in frozen solutions or vapor-deposited matrices is achieved by using exciting light whose bandwidth (0.01-0.1 cm-1) is less than that of the inhomogeneously broadened absorption band. Lasers are optimal in this respect. The spectral bandwidths can then be minimized by selective excitation only of those fluorophores that are located in very similar matrix sites. The temperature should be very low (5 K or less). The techniques based on this principle are called in the literature site-selection spectroscopy, fluorescence line narrowing or energy-selection spectroscopy. The solvent (3-methylpentane, ethanol-methanol mixtures, EPA (mixture of ethanol, isopentane and diethyl ether)) should form a clear glass in order to avoid distortion of the spectrum by scatter from cracks. 

Figure 13. (a) Relative blue pulse peak powers from bulk appKTP and bulk KNb03 crystals, (b) Dependence of SHG efficiency on fundamental spectral bandwidth of femtosecond Cr LiSAF laser. 

---