Matthew D. Rannals
Detecting Carbon Disulfide Gas in a Binary Mixture with Air Using Optoacoustic Techniques

Trace amounts of Carbon Disulfide gas were detected in test cells through the use of an optoacoustic spectroscopy technique. Commercially produced quartz test cells of lengths 10mm, 20mm, 50mm, and 100mm were used to contain the Carbon Disulfide gas. A Nitrogen laser which emitted 800 picosecond pulses was focused inside a test cell in order to get maximum absorption of energy from the laser beam by the gas molecules. In addition, the laser had a wavelength of 337 nanometers which corresponded to a strong optical absorption band in Carbon Disulfide. The pulsing quality of the laser beam created a periodic pattern of heating and cooling within the gas volume. This pattern resulted in the production of an acoustic wave, since the changing temperature of the gas corresponds to a periodic change in pressure which is detected by a microphone attached to the cell wall. Signal strength was increased by the sound waves resonating in the test cells, allowing measurements to be taken as the concentration of Carbon Disulfide decreased.