Optical multichannel detector

Unfortunately (alas, not uncommonly), the significance of the optical multichannel detector has as yet escaped most potential users, who erroneously consider it a mere curiosity still emerging from its embryonic stage. This manuscript is another attempt to demonstrate the maturity and viability of the optical-multichannel detection approach. No longer is the technique a novelty toyed with by a handful of curious instrumentalists, but rather a readily available scientific tool whose performance characteristics and spectrometric applicability are relatively well understood. 

The use of optical multichannel detectors in studies of optical phenomena with various time durations... 

In the time resolved Raman measurements on radiation-chemical systems, optical multichannel detection offers some distinct advantages over the photon counting techniques. The intense Cerenkov pulse associated with the electron pulse is intense enough to saturate a photomultiplier tube (PMT). In an optical multichannel detector, the Cerenkov pulse can be effectively gated off by turning the detector on within a few nanoseconds after the electron pulse is over. Apart from this, such spectra are free from the variation in electron or laser pulse intensity unlike the spectra obtained by single channel devices. 

Picosecond spectroscopy enables one to observe ultrafast events in great detail as a reaction evolves. Most picosecond laser systems currently rely on optical multichannel detectors (OMCDs) as a means by which spectra of transient species and states are recorded and their formation and decay kinetics measured. In this paper, we describe some early optical detection methods used to obtain picosecond spectroscopic data. Also we present examples of the application of picosecond absorption and emission spectroscopy to such mechanistic problems as the photodissociation of haloaromatic compounds, the visual transduction process, and inter-molecular photoinitiated electron transfer. 

A. C. Eckbreth, Optical Splitter for Dynamic Range Enhancement in Optical Multichannel Detectors, Appl. Opt. 22 2118 (1983). 

Multichannel Raman spectrometers are similar to the conventional systems except that the photomultiplier tube is replaced with an optical multichannel detector... 

An optical detector with appropriate electronics and readout. Photomultiplier tubes supply good sensitivity for wavelengths in the visible range, and Ge, Si, or other photodiodes can be used in the near infrared range. Multichannel detectors like CCD or photodiode arrays can reduce measurement times, and a streak camera or nonlinear optical techniques can be used to record ps or sub-ps transients. 

Topics which will be presented in this chapter include the hardware, software, automation, valve and column configurations, and integration used in comprehensive 2DLC. Aspects of the 2DLC experiment in conjunction with multichannel detectors such as UV diode array optical detectors and mass spectrometers are discussed along with the handling of the data, which is expected to expand in scope in the future as chemometric methods are more widely used for data analysis. 

Let us assume that, in all cases, the optical arrangement is properly optimized, for bringing IR flux both from the source to the sample and from the sample to the detector, with all necessary matching. To estimate the spectral flux on the detector, one needs, first of all, to know the flux emitted by the source. If the spectral flux of the source Fsrc is known, then the average spectral flux reaching one pixel of a multichannel detector can be estimated as... 

The tail of the plasma formed at the tip of the torch is the spectroscopic source, where the analyte atoms and their ions are thermally ionized and produce emission spectra. The spectra of various elements are detected either sequentially or simultaneously. The optical system of a sequential instrument consists of a single grating spectrometer with a scanning monochromator that provides the sequential detection of the emission spectra lines. Simultaneous optical systems use multichannel detectors and diode arrays that allow the monitoring of multiple emission lines. Sequential instruments have a greater wavelength selection, while simultaneous ones have a better sample throughput. The intensities of each element s characteristic spectral lines, which are proportional to the number of element s atoms, are recorded, and the concentrations are calculated with reference to a calibration standard. 

Figure 1. Experimental system used in the time resolved absorption measurements. (EL=excimer laser, KrF, 248nm DG=delay generator OMA=optical multichannel analyser MC=monochromator and gated diode array detector C=cell X=xenon flash lamp L=lenses )...

The second promising method is the use of the spectrum of a diatomic or larger molecule. As discussed in Section II-C, if one can describe accurately the population distribution for the molecule under excitation conditions, then the temperature can be extracted from the measured spectrum. The difficulty lies in capturing the spectrum in a sufficiently short time period. This can be accomplished through the use of a multiple detector array, or Optical Multichannel Analyzer such as is manufactured by Princeton Applied Research Co. (30). 

Figure 5. Fiber-optic vidicon spectrometer. (1) Nitrous oxide/acetylene flame (2) SIT vidicon detector (3) Fiber-optic input lenses (4) Fiber-optic entrance slit system (5) 0.5-m Czemy-Turner monochromator (6) Optical multichannel analyzer (7) Oscilloscope display.

Versatility of an Optical Multichannel Analyzer as an HPLC Detector... 

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