Transmittance spectrum dispersed

It is interesting to note that the simultaneous time and frequency resolution of the dispersed transmittance spectrum /d is not limited by the well-... 

In practice, it turns out to be advantageous to calculate the spectrum uj, At) of the impulsive polarization, that is, the Fourier transform of P t, At) with respect to t. The physically appealing feature of P (w, At) is that this quantity can be viewed as the generalization of the linear absorption spectrum of a stationary state to the transient absorption spectrum of a nonstationary state.Inserting (44) into Eq. (9), the dispersed transmittance spectrum for finite probe pulses can be written as °... 

Figure 5 UV- %ible transmittance spectrum of CuS dispersed films with precursor film composition of a, CuCl2-2H2O/HPC=0.253/0.5(g/g) b,CuCl2-2H20/HPaSi02 sol=0.5/0.4/0.29(g/g) c, CuCl2-2H20/HPCySi02 sol/AlCl3=0.5/0.5/0.29/0.2(g/g).

Figure 5 shows a fluorescence spectrum of perylene (Pe) in a single tri-n-butyl phosphate (TBP) droplet (r = 1.5 fxm) dispersed in water. Although the spectral band shape shorter than 450 nm is somewhat distorted owing to a change in transmittance of the beam splitter of the microscope (Figure 3)... 

Most spectroscopic measurements involve the use of an appropriate combination of source, dispersive device, and detector to analyze the absorption or emission spectrum of a sample. If only the wavelength or frequency of the radiation is measured, the resultant instrument is called a spectrometer. If the instrument provides a measure of the relative intensity associated with each wavelength, it is called a spectrophotometer, but this fine distinction is often ignored. Absorption spectra are often characterized by the transmittance Tat a given wavelength this is defined by... 

Generally, the assumption is made that scattering does not depend on the wavenumber so that the conversion of the measured reflectance spectrum R by means of the Kubelka-Munk function F R), results in an absorption-proportional representation. As for ATR and reflection-absorption spectroscopy, also the diffuse-reflectance spectmm does not consist of dispersion features but band-like structures. For changes in low absorption, the sensitivity of diffuse reflectance is greater than the one of transmittance, while strong absorption bands are less pronounced in the diffuse-reflection (see Fig. 6.4-18). Therefore, diffuse-reflection spectra resemble poorly resolved transmittance spectra. For diffuse reflectance spectra where R is in the order of 0.01 or below, the function -log R or just I / R is equally well suited for conversion (Olinger and Griffiths, 1988). Such level are found with compact samples such as polymer foams or varnishes with filler (Otto, 1987 Korte and Otto, 1988). 

Fig. 3. Two-dimensional MQNMR spectrum of 3-chloroiodobenzene (2) oriented in liquid crystalline solution with non-selective excitation and detection (Fig. 2). 1,024 increments in fu 12 scans per increment, 48 kHz in f2, 160 kHz in j, 400 MHz at 295 K, transmitter offset 18 kHz from the centre of the 1H spectrum. The transmitter offset was set to provide dispersion between the various MQ spectra.

Figure 10.11 Non-dispersive analyser for measuring CO2 in gaseous media. This assembly is representative of many portable detectors. The selectivity is assured by an adapted optical illter (F2) and by a membrane at the entrance to the cell which only permits gas to pass through to the detector. The assembly contains a second filter (FI) chosen in a non-absorption zone which authorizes to a computation of the transmittance. On the diagram are shown the bandwidths of the two filters and the spectrum as function of transmittance of a gas, here COj. The detectors are thermistors. Left, a chart which presents a choice of wavelengths in the mid-IR and the near IR for several gases (reproduced courtesy of Edinburgh Sensors, GB).

Zero-order phase correction is even easier to understand. It lines up the phase of the receiver with the phase of the transmitter so that a resonance that is exactly on resonance will appear purely absorptive—i.e., with no dispersive character. Zero-order phase correction affects every resonance in the entire frequency spectrum by the same amount. 

Filter spectrophotometer A spectrophotometer that uses filters of fixed, narrow band-pass transmissions of discrete wavelengths spaced across the spectrum, to measure the transmittance or reflectance of materials at these discrete wavelengths. The resulting special data arranged in order constitute an abridged spectrophotometric curve. Thus, the series of filters replaces the dispersion monochromator used in a continuous spectrophotometer. Willard HH,... 

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