Spectrometry high aperture

Large aperture, high resolution spectrometry can be achieved using interferometers. A scanning system used in conjunction with Fourier transform spectroscopy (see Section 3.4) would facilitate the rapid measurement of complex spectra. As computer facilities are essential, the technique lends itself to automated analysis. 

The combination of HPLC and mass spectrometry was impossible for many years due to the difficulty in removing the solvent prior to the analyte entering the high vacuum of the mass spectrometer. However, with the advent of the atmospheric pressure ionization techniques discussed previously, the two instruments have been combined to give the relatively new technique of LCMS. The eluant from the HPLC is passed into one of the atmospheric pressure ion sources, where ions are produced and most of the solvent is rapidly evaporated. The ion cloud then passes through a small aperture into the vacuum of the mass spectrometer, where the solvent is totally removed, and the ions can be focused and mass analyzed in the normal manner. 

Atmospheric-pressure ionization mass spectrometry (Horning et al., 1973 Carroll et ai, 1974) is a chemical ionization procedure that differs from the standard technique in a number of ways. The reaction chamber (ion source) is at atmospheric pressure and is external to the high-vacuum region of a quadrupole mass analyser. Ions and molecules enter the mass analyser region through a small aperture. The ions are obtained by ion lenses, while... 

Fig. 6.9 Schematic view of the lA-TOF system. Gas-phase sample molecules are ionized by alkali metal ion attachment and become adduct ions in the lA ion source. The adduct ions are extracted through the aperture into the differential pumping region, pass through the skimmer, and are introduced into the TOF mass spectrometer. Because 100 Pa of gas is introduced into the lA ion source, a differential pumping system is used to evacuate the gas since the TOF mass spectrometer must be kept in a high vacuum condition. The orthogonal acceleration reflector TOF mass spectrometer realizes mass spectrometry with a high mass resolution over a wide mass range. (Reprinted with permission from Ref [88]. 2007, John Wiley and Sons)...

C Bremard, P Dhamelincourt, J Laureyns, G Turrell. The effect of high-numerical-aperture objectives on polarization measurements in micro-Raman spectrometry. Appl Spectrosc 39 1036-1039, 1985. 

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