Delayed stages

Manchester A variation on the Ferrox process for removing hydrogen sulfide from industrial gases in which several absorbers are used, and delay stages permit completion of the reaction with the iron oxide absorbent. Developed by the Manchester Corporation Gas Department in the 1940s and installed in several British gasworks. 

A distinctive feature of the kinetics of a reaction in a flame is the freedom of the reaction from any delaying stages whereas in self-ignition the stages of accumulation of heat in the system and of active centers delay development of the process, in a flame there is no slow accumulation of heat. 

Figure S> Schemaiic layout of an ultrafasl puaip-probe spectrometer. Top left panel A cw diode-pumped, Frequency-doubled, Nd YAO laser B mode-locked Ti-S oscillator C regenerative Ti-S amplilier D Q-switched, frequency-doubled Nd YLF amplifier pump laser E second/third-iiarmonic generators or OPA. Lower right panel F continuum generation G sample H CCD spectrograph. The double arrow indicates the optical delay stage, and the dashed tine indicates the pump-beam trajectory.

The apparatus employs a passively mode locked Nd/YAG laser oscillator, a Pockel cell pulse extractor, and Nd/YAG laser amplifier to produce laser pulses at 1064 nm. Non-linear crystals convert 30% of this light to 355 nm, which is used for excitation of the sample. The optical path length of the 355 nm light is varied by a computer-controlled time delay stage. 

To time resolve the nonlinear refraction of a purely refractive material a closed-aperture Z-scan is performed at a fixed time delay to determine the Z positions of the peak and valley of the transmittance. With the sample fixed at the peak Z position the time delay stage is scanned. This step is repeated with the sample at the valley Z position. The difference between these two time-dependent curves is A7 p.y( j), which is directly proportional to the nonlinear phase change. 

A deficiency of the above reaction scheme is that it does not properly account for the initial delay stage observed with many accelerated sulphur curing systems. In a linked series of papers Coran (1964, 1965) and Campbell and Wise (1964) developed a model reaction scheme largely substantiated by their experimental observations. 

Assuming that each of the electron transfer stages follows the regularities of a delayed discharge, determine a theoretical value of a Tafel s slope of polarisation characteristics depending on a number of a delayed stage. 

With 100-fs pump and probe pulses, the effective time resolution of the ultrafast spectrometer, i.e., the rise time of an instantaneous signal, is ca. 300 fs. The temporal chirp over the 450-750 nm range of the white light probe pulse is ca. 200 fs. The maximum temporal window of the experiment, limited by the optical delay stage dimension, for commercially available system goes from 0-1,000 ps to 0, 000 ps. 

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