The Effect of Internal Relaxation on Optoacoustic Conversion in Liquids.
MISSISSIPPI UNIV UNIVERSITY PHYSICAL ACOUSTICS RESEARCH LAB
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In the optoacoustic effect, optical energy is adsorbed by a medium and converted to translational energy, creating an acoustic signal. In most liquids, the conversion process takes place very rapidly ps or fs and the nonradiative decay time is much shorter than the resulting acoustic signal. Theories have been developed, based purely on geometrical considerations, which accurately predict the optoacoustic signal in such cases. The results show that for a short pulse of optical energy the time dependence of the acoustic pressure is determined by the size and shape of the excitation zone. This research was concerned with the actual energy transfer process and how variations in the process which exist from one liquid to another will affect the optoacoustic signal. The purpose of this study was to observe the optoacoustic signal in a situation where nonradiative decay is slow enough to compete with the geometry of the excitation zone in determining the time dependence of the acoustic pressure, and to develop a model to predict the signal in such a situation.
- Physical Chemistry