McPherson’s Ultimate Triple 3 (UT3) Spectrometer delivers better imaging performance and stray light rejection for Raman spectroscopy at wavelengths from 190 to 800 nm. The UT3 delivers excellent Raleigh rejection of about 1 or 2 cm -1 in the Visible. Performance is attained by using small entrance images, high quality off-axis parabolic optics, and a unique relay / spatial filter stage located in the middle of the subtractive pre-monochromator.
Photo below left shows the triple monochromator system without the reflective entrance optics. Below right the reflective collection system.
>Reflective optics with optimized coatings provide response in the ultraviolet. For Raman work across a wide wavelength range, optimized for the UV and for superior rejection, the Ultimate Triple 3 Spectrometer is a stand out. McPherson’s UT3 has the following features: The entire optical train uses reflective optics to enable the wide wavelength range without refocusing. The f/1 collector is a high quality reflective parabolic system designed by Dr. M. Ruebhausen (University of Hamburg) and built by McPherson. It uses master Lambda/8 parabolic reflectors for 6X magnification, sample to slit. The high performance subtractive double pre-monochromator is used for band selection and edge formation. The pre-spectrometer utilizes master Lambda/8 off-axis parabolic optics for idyllic point imaging. The slits translate to fine tune the spatial location of images and optimize the rejection. The unique subtractive stage also uses a relay / spatial filter stage, further sharpening the rejection edge.
The high resolution and aperture matched spectrograph stage, with elliptical imaging optics, optimizes flux conservation and imaging across a larger focal plane. A simple single stage bypass allows use of simple filters with the spectrograph for feasibility or preliminary works. This is the third generation of successive improvements to an original concept by Dr. Miles V. Klein (University of Illinois – Urbana).
Specifications
| Focal Length | First stage: 400 mm, Second stage: 400 mm, Third stage: 670 mm |
| Slit Locations | Axial and lateral with optional extra entrance and exit port selection mirrors |
| Slits | 0 to 4 mm wide; 2 to 20 mm high |
| Slits (Subtractive intermediate) | 0 to 10 mm wide; 0 to 10 mm high |
| Slits (Spectrograph entrance) | 0 to 4 mm wide; 0 to 20 mm high |
| f / No. | f/5.6 |
| Dispersion | 0.83 nm/mm with 1200-g/mm (direct to single or subtractive double) |
| Resolution | 1 cm^-1 at 500 nm; 3.5 cm^-1 at 240 nm |
| Grating Size | 68-mm² and 120 x 140-mm; select from many gratings including original (master) high fidelity holographic gratings |
| Drive Mechanism | Sine bar |
| Step Size | 0.00009 nm |
| Wavelength Accuracy | +/-0.2-nm (on counter, with 1200 G/mm grating) |
| Wavelength Reproducibility | +/- 0.005 nm (with 1200 G/mm grating) |
| Focal Plane | 50-mm, multiply dispersion by the width of your detector for range |
| Wavelength Range | refer to grating of interest for range |
Spectral Resolution and Coverage
|
Configuration |
Single (direct or double filter stage) |
|
|
Grating(g/mm) |
Mechanical Range |
CCD Coverage (1'') ** |
|
300 |
0-6000 nm |
137 nm |
|
600 |
0-3000 nm |
68 nm |
|
1200 |
0-1500 nm |
34 nm |
|
1800 |
0-1000 nm |
23 nm |
|
2400 |
0-750 nm |
17 nm |
|
3600 |
0-500 nm |
11 nm |
**1 nm corresponds to ca.
170 cm־¹ at 240 nm
40 cm־¹ at 500 nm
15 cm־¹ at 750 nm
Below, full spectrum of Sulfur with excitation wavelength 457 nm, 1 second integration, laser power in spot 3.5 mW. The spectrum is raw data, was not corrected. Also, Sulfur with excitation wavelength 457 nm showing the low energy tail. The vertical black lines indicate different pass bands, yielding a cut-off of around 6 wavenumbers.
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