Slit width spectral

FIGURE 3.3. Infrared spectrum of cyclopentanone in various media. A. Carbon tetrachloride solution (0.15 M). B. Carbon disulfide solution (0.023 M). C. Chloroform solution (0.025 M). D. Liquid state (thin films). (Computed spectral slit width 2 cm-1.)... 

Spectra were obtained with a Perkin-Elmer Model 13 spectrophotometer (double beam) modified to scan and record linearly in frequency [9]. A calibrated LiF prism was used with estimated frequency accuracy rh 4 cm"1. The spectral slit- width was about 9 cm "1 at 3600 cm"1 and 6 cm"1 at 3000 cm 1v Transmission accuracy is estimated at 0 5% in the region 30-50% T, where most measurements were made. The zero and 100% transmission values were measured for each spectrum, and a correction was applied for false energy. 

For the study of the first overtones of the O—H, N—H, and C—H bonds, situated in the range from 8000 to 5500 cm-1 we used a double beam recording autocollimating spectrophotometer with glass prisms, similar to that described before [19, 22] and constructed in the laboratory. The recording was photographic. The spectral slit width was 15 cm-1 at 7000 cm-1. 

Spectra were run on a Perkin-Elmer model 125 grating spectrophotometer at room temperature, ignoring the heating effect of the IR beam. Reference beam attenuation was used. The spectral slit width was less than 3 cm-1 in the region 1600-1400 cm-1. Optical density measurements were carried out as previously described (19). 

Structural Determinations. Wafers containing 1.5 mg of zeolites in 1 gram of KBr were used. Spectra were scanned on a Perkin-Elmer model 225 grating spectrophotometer with a spectral slit width of ca. 3 cm-1. 

Fig. 11.6 Resonance Raman spectra of compound III of horseradish peroxidase (0.2 mM) in 10 mM phosphate buffer, pH 7.8, containing 30% v/v methanol at — 10°C excited at three different wavelengths. Instrumental conditions spectral slit width 5 cm-1 laser power, 30 mW acquisition time, 40 min. Reproduced with permission from [139]...

Spectral slit-width Wavelength Background corrector Gas flow ... 

Figure 2. Visible emission spectrum from the chemiluminescent reaction of ozone with ethylene at room temperature (uncorrected for spectral sensitivity). Total pressure 0.4 torr flow rate of 0 /02 is 30 cc/min flow rate of ethylene 5 cc/min spectral slit width 10.6 nm.

Infrared Spectral Measurements. Sample preparation techniques and apparatus have been described previously (3, 4). The spectra were recorded on disks of powdered material with a Cary-White Model 90 infrared spectrophotometer. Spectra were obtained from 4000 to 1200 cm" at a spectral slit width of 4 cm" and a scan speed of 3 cm Vsec. The infrared cell was so constructed as to permit calcinations to be done... 

Spectrometer with spectral slit widths ranging from 0.4 to 0.2 cm by Berney ( ). 

Laser lUman spectroscopy (LRS). The spectra were recorded on a Nicolet 950 FT-Raman spectrometer instrument, equipped with a nitrogen cooled Ge detector. A Nd YAG laser (1064 nm) was used as excitation source. The measurements were performed with a power at the sample of 100-200 mW in order to avoid decomposition and thermal effects. The samples were rotated to provide a noncontinuous irradiation of any given spot on the samples. The spectral slit width was typically 4 cm". ... 

Fig. 19. Resonance Raman spectrum of Wolffram s red (see previous caption) at ca. 80 K, = 514.5 nm, spectral slit width ca. 2 cm". (From Clark and Turtle, Ref. (93)]...

The spectral range of interest for AAS spans from the near infrared (852.1 nm for Cs) to the vacuum ultra violet (193.6 nm for As). A monochromator is a device which separates, isolates, and controls the intensity of a narrow region of the radiant energy which is transmitted to the detector (characterised by its spectral slit width). It consists of an entrance slit, a dispersing unit (a diffraction grating) and an exit slit. The greater the intensity of the radiation transmitted to the detector the lower the signal amplification required (which contributes to electronic noise). However, the entrance and exit slits must be of similar mechanical widths (aperture size) so that, in practice, a compromise must be chosen (slit width versus narrow... 

Figure 6 The influence of spectral slit width on AAS calibration curves for silicon using each of the six spectral emission lines between 250 and 253 nm (A). Provided that a sufficiently narrow spectral slit width is used, linear calibration plots are obtained at each (B), however at 251.61 nm, as the slit width is increased, calibration plots become increasingly curvilinear (C). An optimum signal/ noise ratio is obtained with a spectral slit width of 0.7 nm (D).

Figure 13. Raman spectrum of anatase natural crystal. Laser power was A50 mW at A880 A. Spectral slit width was 4 cm l. Reproduced with permission from Ref. 153. Copyright 1972 Appl. Spectrosc.

If the intensity of the source and the sensitivity of the detector are sufficient, the spectral purity can be improved (the bandpass decreased) by decreasing the slit width. The decrease may not be hnear, however, and a limit is reached due to aberrations in the optics and diffraction effects caused by the slit at very narrow widths. The diffraction effectively increases the spectral slit width. In actual practice, the sensitivity limit of the instrument is usually reached before diffraction effects become too serious. 

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