Crossed-dispersion

Wu [79] has suggested that the cross-dispersion as well as the cross-polar interactions are more appropriately expressed using harmonic rather than geometric means, so that... 

We have observed three subgiants HD 23249 (KO), HD 198149 (KO), HD 222404 (Kl) and three dwarfs HD 10780 (KO), HD 4628 (K2), HD 201091 (K5), on 2002 November 28 and 29, with the high-resolution cross-dispersed echelle spectrograph SOFIN, mounted on the Nordic Optical Telescope (NOT). They are in the solar neighbourhood (< 15 pc), are very bright (V < 6) and have modest projected rotational velocities (v sin i < 4 km s 1) to limit blends between spectral lines. They also do not present any evidence for emission (or a moderate one, as in the case of the three dwarfs) in the core of Ca II H and K lines. 

One optical arrangement in an echelle-based monochromator. In this case a Schmidt cross-disperser is used to disperse the UV light instead of The prism which is used for visible light only. This results in better transmission in the UV (reproduced with permission from the Perkin Elmer Corporation). 

All the above dispersions lead to droplets. These droplets must be transformed into solid like particles by a stabilization process. Table 1 provides the most usual encapsulation technologies by crossing dispersion methods and stabilization methods. Table 1 is not an exhaustive list. 

Due to its versatility, robustness, and relativel low cost, ICP-AES has started to be considered as routine instrumentation for elemental composition measurements in many laboratories involved in food analysis. Unquestionably, the acceptance of the technique has been further advanced by the commercial availability of rapid, simultaneous, and flexible, sequential instruments based on echelle grating crossed dispersion and solid state detectors. It is expected that novel nebulizer devices for liquid sample introduction will find increased applications in beverage analysis. 

Image dissector tubes (Fig. 26) make use of an entrance aperture behind the photocathode, by which the photoelectrons stemming from different locations of the photocathode can be scanned and measured after amplification in the dynode train, as in a conventional photomultiplier. Although used in combination with an echelle spectrometer with crossed dispersion for flexible rapid sequential analyses [59], these systems have not had any commercial breakthrough. This might be due to the limited cathode dimensions but also to stability problems. 

In addition, Echelle spectrometers are often used [50], By combination of an order-sorter and an Echelle grating either in parallel or in crossed-dispersion mode, high practical resolution (up to 300 000) can be realized with an instrument of fairly low focal length (down to 0.5 m) (Fig. 94). Therefore, the stability as well as the luminosity are high. By using an exit slit mask with a high number of preadjusted slits, highly flexible and rapid multielement determinations are possible. 

The spectrometer used is a modified Spectrametrics Spectraspan III echelle grating spectrometer with a quartz prism cross disperser. An echelle spectrometer was chosen because of its two dimensional format display. This format allows efficient simultaneous examination of a much wider spectral range than with a linear dispersion spectrometer when a two dimensional television camera type detector is used. 

Figure 2.27 An echelle spectrometer optical layout. The eohelle grating disperses the light to a second wavelength selector, called a cross disperser. The cross disperser may be a prism or a conventional grating. [ 1993-2014 PerkinElmer, Inc. All rights reserved. Printed with permission.

Coupling with crossed-dispersion echelle spectrometer possible. MCP = MicroChannel plate. 

Figure 10 Diagram of the echelle spectrograph developed by Pelletier [133] SI, entrance slit LI, collimating lens Ml, mirror CD, cross-disperser (grating) EG, echelle grating L2, focusing lens FP, spectrograph focal plane. (Adapted with permission from Ref. 133.)...

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