Vacuum ultraviolet sources

Ever brighter vacuum-ultraviolet sources are being developed that would further boost SPI sensitivity, which already is typically 10 useful yield general, sensitive elemental analysis would then also be available using SPI, making possible a single laser arrangement for both elemental and molecular SALE... 

A photoionization detector uses a vacuum ultraviolet source to ionize aromatic and unsaturated compounds, with little response to saturated hydrocarbons or halocarbons. Electrons produced by the ionization are collected and measured. 

Marshall, T. C. (1985). Free-Eleclron Lasers, Macmillan, New York. Reintjes, J. F. (1985). Coherent idlraviolet and vacuum ultraviolet sources. In Laser Handbook, (M. Bass and M. L. Stitch, eds.). North-Holland, New York. 

As for the far-infrared, absorption by air in the vacuum-ultraviolet (VUV) necessitates evacuation of the optical path from source to detector. In this region it is oxygen which absorbs, being opaque below 185 nm. 

Despite the first prediction [34] of a measurable PECD effect being a few decades old, it is only in the last few years that experimental investigations have commenced. Practical experiments have needed to await advances in experimental technology, and improvements in suitable sources of circularly polarized radiation in the vacuum ultraviolet (VUV) and soft X-ray (SXR) regions needed for single-photon ionization have been been key here. In the meantime, developments in other areas, principally detectors, also contribute to what can now be accomplished. 

Perhaps all the elements present in the periodic table might be excited to yield respective emission spectra by employing a huge energetic source. However, it has a serious drawback because most of the spectral lines invariably fall within the vacuum-ultraviolet region thereby rendering their critical studies rather difficult. Hence, the emission spectroscopy is exclusively limited to metals and metalloids. The non-metals, for instance Phosphorus, Sulphur, Carbon etc. are not limited to these studies. 

There have been remarkable advances in synchrotron radiation research and related experimental techniques in the range from the vacuum ultraviolet radiation to soft X-ray, where the most important part of the magnitudes of these cross-section values is observed, as shown below. Therefore, it is also concluded that synchrotron radiation can bridge a wide gap in the energy scale between photochemistry and radiation chemistry. Such a situation of synchrotron radiation as a photon source is summarized in Fig. 1 [5,6]. 

The light sources used for CD measurements must be intense and should possess good short-term stability. Synchrotron radiation promises to be an excellent source of radiation for CD measurements in the wavelength range from vacuum ultraviolet to infrared 247, 248). 

CIO and BrO abundances are detected simultaneously and continuously as the airstream passes through the instrument. They are not detected directly but are chemically converted to Cl and Br atoms by reaction with reagent nitric oxide gas that is added to the airstream inside the instrument. The Cl and Br atoms are then detected directly with resonance fluorescence in the 2D5/2 -> 2P3/2 transitions in the vacuum ultraviolet region of the spectrum. In resonance fluorescence, the emissions from the light sources are resonantly scattered off of the Cl and Br atoms in the airstream and are detected by a photomultiplier tube set at right angles to both the light source and the flow tube. The chemical conversion reactions... 

Rare-gas samples exist only at cryogenic temperatures and most of the optical spectroscopy of electronic processes should be done in the vacuum ultraviolet. Making experiments requires an indispensable combination of liquid-helium equipment with windowless VUV-spectroscopic devices and synchrotron radiation as a photon source. To study the electronic excitation energy pathways and a variety of subthreshold inelastic processes, we used the complimentary advantages of cathodoluminescence (possibility to vary the excitation depth beneath the sample surface), photoluminescence (selective-state excitation by synchrotron radiation at high-flux SUPERLUMI-station at HASYLAB, DESY, Hamburg) and... 

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