@Article{ChemPhys_324_653, author = {A. Urakawa and T. B{\"u}rgi and A. Baiker}, title = {{Kinetic analysis using square-wave stimulation in modulation excitation spectroscopy: Mixing property of a flow-through PM-IRRAS cell}}, journal= {Chem. Phys.}, ISSN = {0301-0104}, volume= {324}, number= {2-3}, pages = {653-658}, eprint= {http://www.unige.ch/sciences/chifi/publis/refs_pdf/ref01088.pdf}, doi= {10.1016/j.chemphys.2005.12.009}, 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{\frac{ }{ }}modulation infrared reflection{\frac{ }{ }}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.}}, year = {2006} }