Reactions of HS Radicals Important in Coal Combustion. Project Status Report, January 1-March 31, 1981

摘要

HS radicals are generated in sizable concentration via the photolysis of H sub 2 S by either an ArF or a KrF laser. The fate of the ground state HS radicals is then monitored by exciting the A exp 2 sigma exp + - X exp 2 PI transition of HS via the laser-induced fluorescence (LIF) technique. Our present experimental set up is basically the same as described previously but with some very important modifications. Essentially, either the ArF or KrF laser is used as the source of photodissociation, and a tunable frequency doubled flash-lamp-pumped dye laser (CMX-4) or a frequency doubled Nd:YAG laser pump dye laser is used as the probe laser. It is important to note that with the addition of the YAG-pumped dye laser system, both the signal sensitivity and time resolution of the detection scheme are improved by better than one order of magnitude because of the short pulse and high energy output characteristics of the YAG laser system. The induced fluorescence signal from the selected radical species is monitored spectrally through a monochromator. Both LIF and the dye-laser signals are averaged in a transient digitizer and are ratioed so that a normalized LIF signal amplitude can be obtained. The delay times between the photolysis laser and the probe laser are varied by a programmable BNC pulse delay generator, and the time delays are determined by the use of a second transient digitizer via optical-triggering devices. Time history of the HS radicals under selected experimental conditions can then be characterized. Both the laser fluences and species concentrations can be adjusted to ensure the measurement of the desired reactive process. All experiments are carried out in a temperature-controllable reaction cell. Results are described briefly. (ERA citation 06:016454)