Optical multichannel analyser

Figure C3.5.3. Schematic diagram of apparatus used for (a) IR pump-probe or vibrational echo spectroscopy by Payer and co-workers [50] and (b) IR-Raman spectroscopy by Dlott and co-workers [39]. Key OPA = optical parametric amplifier PEL = free-electron laser MOD = high speed optical modulator PMT = photomultiplier OMA = optical multichannel analyser.

Por IR-Raman experiments, a mid-IR pump pulse from an OPA and a visible Raman probe pulse are used. The Raman probe is generated either by frequency doubling a solid-state laser which pumps the OPA [16], or by a two-colour OPA [39]. Transient anti-Stokes emission is detected with a monocliromator and photomultiplier [39], or a spectrograph and optical multichannel analyser [40]. 

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 )...

AT/T measurements over the entire pulse bandwidth are performed using an optical multichannel analyser. In all measurements, the maximum signal is a few percent and linearity is verified to avoid saturation effects. 

A spectrometric set-up to measure transient spectra in the subpicosecond range is shown in Fig. 12. Half of the amplified pulses from the subpicosecond laser (L) is split into a cell of H20. The residual pulses pass through a variable delay line and are focused to excite the sample (beam 2). The delay is automatically scanned by a stepping-motor-driven stage (M). The emerging continuum beam is split into two parts (beams 0 and 1). Both are focused into the sample (E) and after that on the entrance slit of a spectrograph (S). The resulting two dispersed spectra are recorded by an optical multichannel analyser (D). The description of the passively mode-... 

Figure C3.1.5. Schematic diagram of an intensifier-gated optical multichannel analyser (OMA) detector. The detector consists of a microchannel plate (MCP) image intensifier followed by a 1024-channel Reticon photodiode array. Light dispersed across the semitransparent photocathode ejects photoelectrons. These are accelerated toward the entrance of the microchannels by the gate pulse. The photoelectrons collide with the channel walls to produce secondary electrons, which are accelerated in turn by the MCP bias voltage to produce further collisions and electron multiplication. Electrons leaving the microchannels are further accelerated by the phosphor bias voltage.

In Fig. 4.31 an example is given controlling a dye laser by one microprocessor and a UVA is-spectrometer by another. These two microprocessors are interconnected via data and control lines. Their programs are synchronised. The first microprocessor controls the spectrometer, the second an optical multichannel analyser, which rapidly takes emission spectra during the time the laser pumps the dye solution. Both have to be synchronised with the spectrometer which takes the absorbance spectra. The laser has to be triggered by the optical multichannel analyser. 

A homemade laser fluorimeter (Fig. 3) has been built for the experiments. The fluorimeter consist of a laser source, optical elements for light conversion, a fiber-optic cable, a cuvette and an optical multichannel analyser. 

Sample handling and preparation is very easy, as in the case of IR spectroscopy. Commercial instruments belong to two main types, conventional scanning and optical multichannel analysers. The main difference between both types is that, in scanning spectrometers, the scattered light is collected and analysed, usually at 1 cm intervals (channels), whereas in optical multichannel analysers a 300-600 cm section of the Raman spectrum, projected on to the detector, is rapidly recorded in a computer memory without... 

IROE-FLIDAR-2 was used (3). The system consisted of a laser source producing a pulse every second with a wavelength of 480 nm and a duration of 15 ns a telescope which collected the radiation from the canopy and an optical multichannel analyser (OMA) which analysed the collected radiation from the canopy at wavelengths over 540 nm to form a spectrum. The... 

S. Jeffers, W. Weller Image intensifier optical multichannel analyser for astronomical spectroscopy . In Adv. Electronics and Electron Phys. B 40 (Academic, New York 1976) p.887... 

Block diagram of the experimental set-up for laser BS=Beam splitter S=sample P=photodiode OMA=Optical Multichannel Analyser. 

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