Article ID Journal Published Year Pages File Type
5377232 Chemical Physics 2006 6 Pages PDF
Abstract
Square-wave stimulation used in modulation excitation spectroscopy [D. Baurecht, U.P. Fringeli, Rev. Sci. Instrum. 72 (2001) 3782] can have significant advantages over a simple sinusoidal-wave due to the high odd-frequency terms contained in square-wave, particularly when a system response is close to linear. Phase-sensitive detection (PSD) affords separating the signals of the different frequency terms with a high signal-to-noise ratio by averaging a number of modulation cycles. A modulation excitation experiment applying square-wave stimulation provides the same information as several experiments applying sinusoidal-wave stimulations at the same frequency as the square-wave stimulation and at higher frequencies. The amplitude and the phase lag of a response obtained by PSD at fundamental and higher frequencies using square-wave stimulation are related to the ones obtained by sinusoidal-wave stimulation using transfer function of a general system. Mixing property of a PM-IRRAS (polarization-modulation infrared reflection-absorption spectroscopy) flow-through cell was studied by a simple mixing tank model using square-wave concentration stimulation. The advantages of square-wave stimulation are shown by the characterization of the mixing property.
Related Topics
Physical Sciences and Engineering Chemistry Physical and Theoretical Chemistry
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