500mm focal length vacuum spectrometer

Seya-Namioka Vacuum Monochromator

The 235 is the McPherson 500 mm focal length Seya-Namioka monochromator. This optical system is housed in a clean stainless steel housing capable of achieving 10-6 torr vacuum. It delivers typical resolution of 0.05 nm with a 1200g/mm grating. An angle of 70° 15' subtends the entrance and exit slit arms. Seya-Namioka mounting maintains all components (slits and gratings) on the Rowland circle. Resolution is maintained over a broad spectral region, astigmatism should be considered depending on the application. The focal length provides increased resolution and work space. Stainless steel construction makes this proven design suitable for use with high vacuum, contaminant free experiments or microchannel plate intensifiers. Wavelengths from 30-nm to 1.2-um can be covered within the scanning range and with appropriate gratings. The 235 is for scanning and microchannel plate intensifier or CCD spectroscopy.

Specifications & Additional Information:


Optical DesignSeya-Namioka
Angle of Incidence35.125 degrees
Focal Length500 mm
Wavelength Rangerefer to grating of interest for range
Wavelength Accuracy+/- 0.10 nm (with 1200 g/mm grating)
Wavelength Reproducibility+/- 0.005 nm (with 1200 g/mm grating)
Grating Size30 x 50 mm (single kinematic grating holder)
SlitsContinuously variable micrometer actuated width 0.01 to 2 mm. Settable height.
VacuumHigh vacuum 10E-6 torr
Focal Plane25 mm microchannel plate or direct detection CCD

Performance with various diffraction gratings:

Grating Groove Density (g/mm) 2400 1200 600 300
Spectral Resolution (nm,FWHM) 0.025 0.05 0.1 0.2
Dispersion (nm/mm) 0.83 1.6 3.3 6.6
Wavelength Range ~30nm up to (nm) 150 300 600 1200
Blaze Wavelength: (nm) holo 70 150 550

* gratings work best from 2/3 to 3/2 the blaze wavelength

Outline Drawing

McPherson Model 235 half meter Seya-Namioka Vacuum Monochromator

Modes of Operation

Model 235 Seya-Namioka with no exit slit for efficient coupling to experiment
UHV 235 for interface to experimental chamber
235 as centerpiece in VUV OC-System
Model 235 works as the emission spectrometer in this optical characterization system
Model 235 Seya-Namioka with no exit slit prepared for scintillated array detector
235 prepared for scintillated detector

The Seya-Namioka is ideal when experiments require more work space around the slits. The large included angle insures that exit or entrance-slits can 'reach' into source chambers or be postioned close by a sample. The Seya also holds up with direct detection array detectors or microchannel plates. For scanning monochromator or spectrograph detection applications the Model 235 delivers a good compromise of instrument size and spectral performance.
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Select Publications

Abstract: Polarization-free excitation cross sections in the extreme vacuum ultraviolet have been measured for electron impact on Ar. Observed spectral features were those lines of ArI and ArII which lie between 700 and 1100 Å. Excitation functions were measured for the ArI resonance line at 1048 Å and the ArII resonance line at 920 Å. Peak cross sections for these two lines were found to be (39.4 ± 7.9) × 10−18 and (6.9 ± 1.4) × 10−18 cm2, respectively. At low energies, excitation of the ArII resonance line is dominated by an electron exchange transition.
James E. Mentall and H. D. Morgan
Abstract: The fluorescence of ND3 has been observed for excitation into the ?←? system at 213.86 nm. The quantum yield for this transition is 8.3×10−5. With this quantum yield and the known rotational linewidth of the upper electronic state, an Einstein A coefficient is obtained that compares favorably with a value calculated from the emission intensity and absorption strength of the (ν1′,ν2′=0,0) ↔ (ν1 ″,ν2 ″ =0,2) vibronic bands. The average of these two values is A=3.6±0.3×107 sec−1. The underlying continuum of the ?←? absorption system, attributed to the predissociation of ND3, is invoked to explain most of the discrepancy between the above value for A and that predicted by the equation of Strickler and Berg. A weaker, more diffuse emission has also been observed from ND3 for excitation into the ?←? system at 206.24 nm with fluorescence quantum yield of 1.1×10−5.
T. A. Gregory and Sanford Lipsky
Abstract: The optical properties of Kapton type H polyimide film, obtained from reflectance measurements, are presented for photon energies from 0.5 to 70 eV. Equations for the energy‐loss function, with parameters fixed by the optical data, are employed to calculate mean free paths and stopping powers for low‐energy electrons (100 eV to 10 keV) in Kapton. The values obtained show good agreement with those predicted by recently proposed analytical formulae for electron mean free paths and stopping powers in solid organic insulators.
E. T. Arakawa, M. W. Williams, J. C. Ashley and L. R. Painter
Abstract: A simple, completely sealed, discharge resonance lamp operated by a 2450 Mc/sec microwave power is described which emits atomic lines of sufficient intensity to be useful as a photochemical light source. When a water impurity is present in the lamp, many emission lines appear in the region of wavelength from 1500 to 2000 Å. These impurity lines can be effectively removed by means of a getter or by a suitable cold trap. The pressures of pure Xe or Kr in the resonance lamp, required to give maximum intensity (approximately 5× 1014 quanta/sec), are 0.7 and 1.0 mm, respectively. The presence of a CO impurity does not affect the intensity of the resonance lines. After passing through a 1-mm LiF window, the intensity of the Xe resonance line at 1295 Å is about 2% of that at 1470 Å and the intensity of the Kr line at 1165 Å is about 28% of that at 1236Å . A mixture of the rare gas and He gives more intense light than the pure gas. The lifetime of the rare-gas resonance lamps is approximately 10 h. Lyman alpha (1216 Å) line from excited atomic hydrogen and a group of lines at 1743–45 Å from excited atomic nitrogen may be used as a photochemical light source.
Abstract: Beam-foil technique has been applied to measurements of radiative lifetimes of 23 terms or levels, all belonging to the 3dn4p (n = 0 to 9) configurations, in Sc(III), Ti(III), V(III), Cr(III), Mn(III), Fe(III), Ni(III) and Zn(III). The experimental lifetimes are in good agreement with lifetimes derived from oscillator-strength calculations, based upon the scaled Thomas-Fermi method, for ultraviolet lines in the spectra of the doubly ionized transition elements.
T. Andersen, P. Petersen
Abstract: Fluorescence spectra of 9-cyanoanthracene polycrystalline films and glasses of different viscosities and polarities are reported. The 490 nm emitting species is identified as the trans excimer. The blue-shift of 9-CNA crystal emission upon increasing temperature is explained in terms of a temperature-dependent competition between two crystal traps giving rise to cis or trans excimer position.
S.E. Morsi, D. Carr, M. Ashraf El-Bayoumi

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