Abstract
Infrared laser photoacoustic spectrometer with a tunable CO, laser and a piezoelectric ceramic detector (PZT) as major constituent elements was developed for the determination of thin organic coatings on metal substrate. Polyvinylacetate film on stainless steel plate was used as a sample and was directly attached to the PZT. Experimental factors which affected the photoacoustic(PA) signals were examined. In particular, the dependence of the PA signals on the incident angles of an excitation laser beam was investigated in detail. As a result, the PA signals were enhanced as the incident angles became larger when the laser beam was polarized. parallel to the plane of incidence. In this case, maximum efficiency was obtained in the angular range of 70°to 80°. The dependence of the PA signals on the thickness of coatings was also examined, and a good linear relationship was obtained between them in the measured thickness range of 10nm to 400nm.
