Sampling optical

Lewis I.R., Griffiths P.R., Raman Spectrometry with Fiber-Optic Sampling, Appl. Spectrosc., 1996 50 (10) 12A - 30A. 

Fig. 3.5. Experimental apparatus for time-resolved THz transmission spectroscopy. The sample is excited with a visible laser pulse delivered by delay line 3. A singlecycle THz electric-field transient probes the polarization response of the sample after time delay tv scanned by delay line 1. The transmitted THz amplitude is monitored via ultrabroadband electro-optic sampling in a THz receiver as a function of time T scanned by delay line 2. From [13]...

Design and selection of the sample interface is vital to provide the best-quahty data for an analysis. The sample interface may be located in the sample cavity of a spectrophotometer, as in the cases of laboratory cuvettes, vials, and flow cells. The sample interface may also be fiber-coupled and located closer to the process. Fiber-optic sample interfaces include flow cells, insertion probes, and reflectance probes. 

To obtain vibrational spectra tuned by external pressure one needs - in addition to the infrared or Raman spectrometer - a special high-pressure optical sample cell, an optical interface between the sample cell and the spectrometer, and a device to measure the pressure on the sample [i]. 

This cosmic spectroscopy method has been extended to study variation of other fundamental parameters. The ratio of the hydrogen atom hyperfme transition frequency to a molecular (CO, CN, CS, HCO+, HCN etc.) rotational frequency is proportional to y = a2gp where gp is the proton magnetic -factor [21]. A new preliminary result here is Ay/y = (—2.4 1.8) X 10-6 about 4 billion light years from us (the average z=0.47). Altogether, we now have 3 independent samples of data two optical samples (see [2,3]) and one radio sample. All 3 samples hint that Aa is negative. 

Background correction and sample measurements are performed consecutively and, unless the original state of the sample is used for background correction, the specimen that is analyzed needs to be exchanged. Hence it is important that filling of material into any sample holder or reactor be reproducible. Specimen manipulation should not affect the relative positions of source, optics, sample holder and detector—these parts must remain in position, or their placement must be well defined. In general, instruments with integrating spheres are less sensitive than... 

Wu Q, Zhang X-C. Free-space electro-optics sampling of mid-infrared pulses. Appl Phys Lett 1997 71 1285-1286. 

Here we look for a solution of the form, HIH,(r, t) = e(n)(r, t)exp(ik r — kost), where k s is different from ks, which is given by a combination of the incoming wave vectors, due to the frequency dispersion of the refractive index of the optical sample. 

Within the slowly varying amplitude approximation, the generated electric field amplitude grows linearly with respect to the distance from the front boundary, z, of the optical sample. Direct integration over z gives the... 

For the design of new, innovative processes to separate low-volatile components such as drugs or polymers with supercritical fluids, experimental data are needed. We designed and built a new apparatus capable of investigating phase equilibria in the occuring complex systems up to 200 bar and 250°C. Phase transitions are determined optically. Samples of the coexisting phases even at high concentration and viscosity are taken. Solid particles can be collected. 

Recently, a new single shot electro-optic sampling technique (Fig. 7) has been developed for the non-invasive characterization of the... 

D. A. Jaworske, K. K. de Groh, T. J. Skowronski, T. McClooum, G. Pippin and C. Bungay, Evaluation of Space Power Materials Flown on the Passive Optical Sample Assembly, NASA Technical Memorandum 209061 (NASA, Washington, D.C., 1999). 

In some cases, these environmental requirements are met by locating the spectrometer remotely from the sampling point, in a cleaner, more controlled environment. Fiber-optic probes, described in Chapter 12, have been used successfully when the sampling point is located 100 m or more from the spectrometer. Depending on the application, fiber-optic sampling may be a critical performance requirement. 

Figure 6.2. Schematic of fiber-optic sampling configuration. Fiber lengths between probe and laser/spectrometer can be quite long, up to several hundred meters.

Pipe with optical sample stream window... 

Various Applications of dispersive Raman coupled with fiber-optic sampling Table 12.4... 

Pure solids, liquids Fiber-optic sampling 22... 

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