Abstract
In this work, a pulsed IR laser is used to excite photothermal deflection signals in gas phase analytes. Characteristics of the lasers, the optical apparatus, and the data processing procedures are analyzed in terms of sensitivities and ultimate precision. Most pulsed lasers have poor longitudinal and transverse mode stability and pointing noise characteristics. Both mode instability and pointing noise result in a spatial intensity distribution at the sample which is not reproduced on a pulse-by-pulse basis.1 Since the refractive-index profile in the sample is related to the intensity profile of the excitation laser, these instabilities can introduce significant errors into the signal. The experimental optimization procedures and data processing methods presented can effectively reduce errors due to pulsed laser mode variations and increase the precision of the measurement by rejection of data obtained from different excitation intensity distributions while modeling the energy response with nonlinear functions. The optical arrangement for these experiments is similar to those described previously.2
© 1986 Optical Society of America
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