Maya2000 Pro Spectrometer Extends to VUV

The Abstract:
Spectral measurements to 153 nm can be achieved easily and economically with the high-sensitivity Maya2000 Pro with Extra-Deep-UV Option. Nitrogen purging of the spectrometer helps to mitigate water and oxygen absorption in the vacuum ultraviolet.

Introduction:
A variety of materials have spectral signatures in the vacuum ultraviolet (VUV) spectral region, typically described as the region from 10 nm-200 nm1, 2. VUV spectroscopy is useful for applications ranging from biomedicine to semiconductor testing. Because the spectral response of standard silicon charge-coupled device (CCD) detectors drops off rapidly at wavelengths as long as 400 nm, and because oxygen and water absorb in the VUV spectral band, maintaining sufficient signal outside a vacuum is not possible. Designing vacuum-compatible spectrometers to address these issues can be difficult and expensive. As a result, most commercially available VUV spectrometers require custom configuration and are too expensive and unwieldy for many common applications.

The Maya2000 Pro with Extra-Deep UV Option is poised to change that. The spectrometer features a 101.6-mm focal length optical bench with a compact crossed Czerny-Turner design and a back-thinned CCD detector that offers superior UV and VUV performance. To minimize signal attenuation inside the optical path, the spectrometer bench is purged with nitrogen, achieving a robust signal for VUV experiments at wavelengths as low as 153 nm.

Experimental Conditions:
To test performance, we started with a Maya2000 Pro configured with a high resolution, UV-enhanced 2400g/mm holographic diffraction grating and a 5 µm slit. The back-thinned detector (Hamamatsu S10420-1106) features a peak quantum efficiency of 75%, with UV quantum efficiencies as high as 50%. A custom magnesium fluoride (MgF2) glass window is placed over the detector for improved transmission over VUV wavelengths.

The test sample for the experiment was a VUV deuterium lamp with a VUV-grade optical window, coupled directly to the spectrometer. We enclosed the source and spectrometer and purged the region with standard laboratory-grade nitrogen.

Results:
Integration time for the measurement was 50 ms. The resultant emission spectrum shows sharply defined spectral peaks at wavelengths as low as 153 nm, with a strong central peak around 161 nm (see Figure 1). The system operated with a spectral resolution of 0.1 nm and a signal-to-noise ratio of 450:1.

We have also used the system to measure a solution containing carbon, hydrogen/deuterium, nitrogen, oxygen, sulfur, chlorine, bromine, silicon and fluorine chromatographically separated into a column and placed in a vacuum chamber with a helium plasma mixture. VUV spectral features were clearly apparent in the spectrum, suggesting a wide variety of short-wavelength applications is achievable.

Conclusions:
The results demonstrate that the reliable and economical Maya2000 Pro can be easily extended to VUV applications. If you have spectroscopy experiments or applications in the VUV, look no further than the Maya2000 Pro as your short-wavelength, affordable, robust solution.

FIGURES

Figure 1:
Emission spectrum of a VUV deuterium lamp shows clearly defined peaks, with good signal-to-noise performance and 0.1 nm (FWHM) optical resolution.


References

1. Wikipedia, http://en.wikipedia.org/wiki/Ultraviolet
Website covers VUV under larger section on ultraviolet light
2. H. Horspool, F. Lenci, CRC Handbook of Organic Photochemistry and Photobiology, (CRC Press, 2003).
3. http://www.oceanoptics.com/Products/maya.asp
Web page at OceanOptics.com with full specifications on Maya2000 Pro

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