Rowland mounting

Abney mounting spect A modification of the Rowland mounting in which only the slit is moved to observe different parts of the spectrum. ab-ne. maunt ir) )... 

Rowland mounting spect A mounting for a concave grating spectrograph in which camera and grating are connected by a bar forming a diameter of the Rowland circle, and the two run on perpendicular tracks with the slit placed at their junction. ro,l3nd, maunt-ir ... 

FIGURE 4-11. Schematic diagram of the Rowland mounting for a concave grating. 

The Rowland mounting is basic to the use of the concave grating but is difficult to use and adjust. For the research that Rowland planned, i.e., measurements of spectral line wavelengths, it was ideal at that time. Other techniques are now available for wavelength measurements, so the purpose of the original Rowland mounting no longer is important and no instruments of this type have been constructed in recent years. 

As WDS analysis is sequential, it is practical to use several spectrometers of this type around the electron column but, for obvious reasons of available space (the diameter of the Rowland circle is approximately 30 cm), we are limited to 2 spectrometers mounted obliquely or 5 vertical spectrometers. The second configuration is generally chosen since it can be used to conduct simultaneous analysis of S elements on the same point. 

Figure 2.6 Basic design of direct reading on a Paschen-Runge mount with fixed optics on a Rowland circle used in simultaneous ICP-AES. (Reproduced by kind permission copyright 1999-2008, all rights reserved, PerkinElmer, Inc.)...

Mountings with a concave grating are also used. Here the radius of the grating determines the so-called Rowland circle. In the direction of dispersion the spectral lines are focussed on the Rowland circle and are monochromatic images of the... 

Figure 7.13 A Rowland circle polychromator. This configuration is called a Paschen-Runge mount. The source shown is an inductively coupled plasma, hut any of the electrical excitation sources can he substituted. Multiple photomultipler detectors are placed at the appropriate positions on the circumference of the circle to measure dispersed wavelengths. [From Boss and Fredeen, courtesy of PerkinElmer Inc. (www.perkinelmer.com).]...

The Wadsworth spectrometer, shown schematically in Figure 4-16, does not make use of the Rowland circle the focal distance is one-half the radius of curvature and another optical element, a concave collimating mirror, is introduced into the optical path. In this arrangement the photographic plate is mounted on a line normal to the concave grating, and thus stigmatic spectra are produced and the dispersion is linear. 

Rowland, R. 1993. Applied Surface Mount Assembly. Van Nostrand Reinhold, New York. 

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