Wavelength nominal

Band of radiation exiting wavelength selector showing the nominal wavelength and effective bandpass. 

A wavelength selector that uses a diffraction grating or prism, and that allows for a continuous variation of the nominal wavelength. 

The spectral resolution of the most monochromatic laser yet devised, expressed as frequency of the laser emission divided by the laser linewidth, is approximately 5 x 10. The laser in question is a special-purpose He-Ne laser with a nominal wavelength of 632.8 nm (15,308 cm l or 4.74 x 10 Hz in frequency units) and a linewidth of 7 to 10 Hz. It is difficult to grasp the physical significance of this degree of resolution. One illustration is that, if the spectrum of this laser were displayed on chart paper such that the zero of electromagnetic energy were located at the sun and 15,308 cm l were located at the orbit of Earth, the width of the peak representing the output of the laser would be 3 millimeters. 

If a mixture of two or more substances is absorbing electromagnetic radiation at the same nominal wavelength, their absorbances will be additive,... 

The half width of the absorption band,h, is the range of wavelengths reaching the sample with at least one half the intensity of the nominal wavelength setting of the instrument. 

Stray radiation, commonly called stray light, is defined as radiation from the instillment that is outside the nominal wavelength band chosen for the determination. This stray radiation often is the result of scattering and reflection off the surfaces of gratings, lenses or mirrors, filters, and windows. When measurements are made in the presence of stray light, the observed absorbance is given by... 

Figure 25-10 illustrates the performance characteristics of a typical interference filter. Most filters of this type have bandwidths of less than 1.5% of the nominal wavelength, although this figure is lowered to 0.15% in some narrow-band filters the latter have a maximum transmittance of about 10%. 

Effective bandwidth The bandwidth of a monochromator or an interference filter at which the transmittance is 50% that at the nominal wavelength. 

After the radiation has been dispersed, a certain portion of it will fall on the exit slit, and the width of this slit determines how broad a band of wavelengths the sample and detector will see. Figure 16.21 depicts the distribution of wavelengths leaving the slit. The nominal wavelength is that set on the instrument and is the wavelength of maximum intensity passed by the slit. The intensity of radiation at... 

Band Nominal wavelength (cm) Frequency (MHz) Magnetic field (gauss)... 

The Air Liquide TDL instrument used in the EAF application employed a TDL operating at a nominal wavelength of 1.56 pm for measurement of CO, H2O, and temperature. The instrument used a pair of H2O absorption features for H2O and temperature measurement and a CO absorption feature for CO measurement. The instrument design incorporates the features listed in Table 14.1 to address the many challenging conditions in this installation. 

In a typical ZoloBOSS installation, a control rack located in or near the plant control room contains multiple laser sources and detectors, diode laser drivers, and a system computer. The light from the individual lasers, ranging in nominal wavelengths between 0.67 and 1.7 pm and tuned to CO, CO2, O2, and H2O absorption features are multiplexed into one single-mode fiber using Zolo s Zmux multiplexer/demultiplexer device. 

Excitation light consisted of an array of 36 leds with a nominal wavelength 660 nm (hansatech LSI light source). 

Figure 10 Idealized slit function. For a nominal wavelength the spectral slit width is I2 - and A4 - A3 is the effective spectral slit width (spectral bandwidth).

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