Bandpass, table

Infrared optics is a fast growing area in which CVD plays a maj or role, particularly in the manufacture of optical IR windows. 1 The earths atmosphere absorbs much of the infrared radiation but possesses three important bandpasses (wavelengths where the transmission is high) at 1-3 im, 3-5 im and 8-17 pm. As shown in Table 16.2, only three materials can transmit in all these three bandpasses single crystal diamond, germanium, and zinc selenide. 

For ease of use and wavelength accuracies of 1-2 nm, organic materials or inorganic ions in solution have been recommended as standards (Table II). However, these must be used carefully because (a) the peak maxima are matrix dependent, (b) narrow Instrumental bandpasses are necessary, (c) impurities may affect peak location, and (d) the peak wavelength values have generally not been certified (11). 

Important performance characteristics of UVA is detectors are sensitivity, linearity and band dispersion. These are controlled by the design of the optics and the flow cell—more specifically by spectral bandpass, stray light characteristics and the volume and pathlength of the flow cell. Specifications of the Waters 2487 detector are shown in Table 3 to illustrate performance levels of modern detectors. 

Table 7.1 are continuous wave (CW), not pulsed. Second, frequency stability to < 1 cm" is important to assure Raman shift precision and avoid line broadening. Although the Raman shift axis is usually calibrated periodically, the laser frequency must remain stable between calibrations. Third, lasers vary significantly in output linewidth, from hundreds of reciprocal centimeters to much less than 1 cm". For the majority of samples of analytical interest, a laser linewidth below 1 cm" is sufficient. Laser linewidths are often quoted in terms of frequency rather than wavenumber, in which case 1 cm" equals 30 GHz. Lasers are available with < 1 MHz linewidths (< 10 em ), but such lasers would be unnecessarily narrow for most analytical Raman applications. Fourth, lasers differ in their output of light at wavelengths other than the laser line itself. Gas lasers (Ar+, Kr+, He-Ne) emit atomic lines (plasma lines), and solid-state lasers luminesce, both of which can interfere with Raman scattering. Essentially all lasers require a bandpass filter or monochromator to reduce these extraneous emissions. 

Table 8.2. Bandpass and Spectral Coverage for Several Single Spectrograph...

We show in the column headed H/D where isotopomers were studied (Y). The spectrometer on which a spectrum was recorded is also reported most of these are described in Table 3.2. If the system has been studied by coherent INS, the references are also included and TAS (triple axis spectroscopy) appears in the instrument column. Much of the early work was carried out on low-bandpass spectrometers that are now defunct, these were generally of the beryllium filter type and are indicated as LBS . 

Table 7.4 shows how, with a flat film set at various distances from a pea lectin crystal (as an example), the numbers of Laue spots, RLPs and overlaps vary. This table shows that there is an optimum distance (64 mm for this unit cell and wavelength bandpass). This optimum arises because as the film is moved further back to reduce the number of spots lost to spatial overlaps eventually this is counterproductive because more spots are lost as they pass beyond the edges of the film. Table 7.5 explores how this optimum distance varies with the spot-to-spot resolution feasible in the data processing computer program. Table 7.6 likewise examines these dependencies for a hypothetical crystal with doubled, pea lectin, cell dimensions, which has eight times more stimulated RLPs. 

Table A3.5. Plane wave (intrinsic) spectral bandpass of reflected beams for perfect silicon and germanium monochromators.

Table 31 Dispersion and bandpass values of a commercial instrument using an echelle grating with 79 groovesmm, with a blaze angle of 6T 26, and having the parent line at the 42nd order. Effective aperture of the spectrometer is f/8. The width of the entrance slit is 80 ptm, and the width of the exit slit is 40 fJm. (Unicam Analytical Systems Ltd.)...

A half-metre grating spectrometer with 25 pm slits typically can give a spectral bandpass or effective resolving power of 0.04 nm in the first order. With the NOA flame, quite useful detection limits for many elements may be obtained (Table 3). Slits of width 10 pm may be used for further line-to-back-groimd discrimination when needed, as for the aluminium 396.1 nm measurement. To correct for backgroimd emission by scanning across a line profile, a wavelength drive at least as slow as 0.2 nm per minute is required. 

In Table 3 some essential parameters are listed, which should be referred to in a manual, since they influence the performance of a spectrometer in addition to such common parameters as range, accuracy, and reproducibility of wavelength, stray light bandpass (spectral bandwidth or slit width of the spectrometer) photometric accuracy, reproducibility, and linearity baseline flatness absorbance zero stability noise level scan speeds response times and data intervals. Furthermore possible modes of the axis are of interest absorbance, transmittance, derivative, Kubelka-Munk function [9], and the possible scaling of the axis. Most of these parameters are given in manuals, determine the limitations of the instrument, and affect each other. 

Combination of f and leads to the absolute rate constants for radiative and nonradiative decay. The values given in Table VII use the set of lifetimes reported by Gelbart et al. There is little discrepancy between the lifetime sets, but since Gelbart et al. used narrower exciting bandpass and since they did not have the nonexponential decay problems with the level 64 reported by Selinger and Ware, theirs may be the preferred set. 

In a bilinear transformation, the variable s in Ha (s) is replaced with a bilinear function of z to obtain H (z). Bilinear transformations for the four standard types of filters, namely, low-pass filter (LPF), high-pass filter (HPF), bandpass filter (BPF), and bandstop filter (BSF), are shown in Table 8.8. The second column in the table gives the relations between the variables s and z. The value of T can be chosen arbitrarily without affecting the resulting design. The third column shows the relations between the analog... 

Formulation PL 6328 (see below) i.a. used in Mk 46 decoy flare [38] has been tested under altitude and dynamic conditions [59]. Table 10.13 displays the spectral efficiency in the 1.7-2.95 pm bandpass range. 

Evidently, we cannot get all of the required background reduction with a cold shield alone, so we will need a spectral filter in conjunction with the cold shield. We pay a penalty for the use of the spectral filter the signal from the blackbody will be reduced. Assume that (like many labs) we have 500 and 800 K blackbodies with apertures that range from 0.050 to 0.500 in diameter, and that total distances from the blackbody aperture to the detector can be as small as 8 . We calculate the irradiance we can expect with three filters, each with a bandpass of 0.2pm, centered at 3, 4, and 5 pm, using two blackbody temperatures (500,800 K) and the two blackbody aperture extremes. Table 9.1 shows the irradiances that we can expect with the 12 different combinations. It also lists the signal-to-noise ratios that we will see, based on the expected NEI. From this table we can pick out the acceptable combinations. 

The monochromator selects and passes only the radiation in a narrow bandpass of known wavelength. This can be done with prisms, or gratings, or a Fourier transform spectrometer. Commercial instruments are listed in a table by Zissis and LaRocca (1978, Tab. 20-7). The same reference discusses the various instrument types in detail. Moore et al. (2009) discuss optical dispersing instruments and provide a table comparing the various types. Shannon and Wyant (1979) also discuss spectral dispersing... 

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