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Model 235 Seya-Namioka Monochromator
for Scanning and MCP or CCD Spectroscopy
- Increased work space
- Internally welded Stainless steel construction
- Precision Micrometer Adjustable Slits
- High resolution
- Gratings rotate about their apex
- Aberration corrected gratings are available
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Model 235 is the McPherson 500-mm focal length Seya-Namioka monochromator. This f/11.4 optical system is housed in a clean stainless steel housing capable of achieving 10^-7 torr base vacuum. It delivers typical resolution of 0.05-nm with a 1200-g/mm grating and operates by simple rotation of the grating about its apex. An angle of 70° 15' subtends the entrance and exit slit arms. The focal length provides increased resolution and work space. Stainless steel construction makes this proven design suitable for use with high vacuum and contaminant free experimental chambers or microchannel plate intensified detectors.
Seya-Namioka mounting maintains all components (slits and gratings) on the Rowland circle. While resolution is maintained over a broad spectral region, astigmatism should be considered depending on the application. The image height at the exit of this instrument is theoretically equal to the height of the entrance image plus 2/3 grating ruled height. Exit images on the order of 25 mm high are not uncommon. When using a photomultiplier (with a large photo cathode area) to scan a source or samples emission, or when using the instrument as a filter for selecting plasma lines from a emission source this presents no problems, If other performance is desired a small selection of aberration corrected gratings are available for improved performance in some wavelength ranges.
Wavelengths from 30-nm to 1.2-um can be covered within the scanning range and with appropriate gratings. The Model 789A-3 digital scan drive can be used for computer control of wavelength settings.
PDF format Data Sheet for the Model 235 Seya Namioka available here
Specifications
McPherson Model 235 500-mm focal length f/11
Vacuum Monochromator / Spectrometer
| Focal Length | 500-mm focal length Seya-Namioka design |
| Angle between Slits | 70° 15' |
| f / No. | 11.6 |
| Grating | 30 x 50-mm ruled area |
| Wavelength Accuracy | +/-0.1-nm (on counter, with 1200 G/mm grating) |
| Wavelength Reproducibility |
+/- 0.005 nm (with 1200 G/mm grating) |
| Focal Plane |
Multiply dispersion by the width of your detector for range |
| Wavelength Range |
refer to grating of interest for range |
Performance of the Model 231 with various gratings:
| Grating (G/mm) (others available) |
2400 |
1800 |
1200 |
600 |
300 |
| Wavelength Range from 30-nm to |
150-nm |
200-nm |
300-nm |
600-nm |
1.2-um |
| First Order Littrow Blaze |
holo |
holo |
holo |
holo |
holo |
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70 nm |
150 nm |
550 nm |
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150 nm |
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200 nm |
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| Resolution (nm) at 313.1-nm |
0.025 |
0.035 |
0.05 |
0.1 |
0.2 |
| Dispersion (nm/mm) |
0.83 |
1.1 |
1.66 |
3.33 |
6.66 |
| The Model 235MX (version number X) is depicted at right. It offers the features of our standard instrument while the housing design offers some unique capabilities. This instrument is fully UHV compatible, has a gate valve on the exit arm, an X-Y-Z adjustable source mount (for optimizing alignment and throughput under vacuum). Not visible in this photo is the reduced diameter slit assembly - provided to extend deep into the experimental chamber from its 2 ¾ cf mounting point. It provides high resolution energy focused at a point close to the sample under test. In cases where source energy must be maintained Imaging and Aberration corrected gratings are available. In source filtering or laser harmonic separation applications the Model 235 has proven desirable. Its working distance and resolution offer the experimenter great flexibility.
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The Model 235 depicted in the diagram below has been integrated into a system utilizing two light sources. The Model 629 hollow cathode and Model 632 Deuterium lamps are used for excitation of samples in the Model 121 sample chamber. Samples under test were excited with selected vacuum UV energy in the 300 - 1600 Å region. The variable angle test reflectance and absorbance capability of the Model 121 was complemented by the addition of an emission wavelength analyzer, a Model 218, 0.3 meter focal length spectrometer with a low energy detector.
