Increasing the Sensitivity to Short-Lived Species in a Modulated Excitation Experiment
| Autor: | Oliver Kröcher, Valentina Marchionni, Alexander Wokaun, Davide Ferri |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Diffraction
Chemistry Analytical chemistry 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Molecular physics 0104 chemical sciences Analytical Chemistry Intensity (physics) symbols.namesake Fourier analysis Modulation symbols Demodulation Sensitivity (control systems) Transient (oscillation) 0210 nano-technology Excitation |
| Zdroj: | Analytical Chemistry. 89:5801-5809 |
| ISSN: | 1520-6882 0003-2700 |
| DOI: | 10.1021/acs.analchem.6b04939 |
| Popis: | The combination of spectroscopic and diffraction methods to study chemical transformations is fundamental for the understanding of reaction mechanisms. The identification of short-lived species, likely active species, is often hindered by the contribution of spectator species not directly involved in the reaction. The present study considers two different approaches to obtain increased sensitivity to transient species for experiments obeying the modulated excitation paradigm and exploiting phase sensitive detection (PSD). First, the variation of the frequency of the external stimulation (ω) during the experiment is considered. We demonstrate using the Fourier analysis that the increase of ω, i.e., the decrease of the modulation period T, enhances the sensitivity to short-lived species. The second alternative is the use of a single stimulation frequency (ω) during the measurement and the variation of the demodulation frequency (nω) during data analysis. The absolute intensity of the phase-resolved signals is reduced by increasing n. However, species with slow kinetics are more attenuated than species with fast kinetics. Thus, transient species possessing fast kinetics are enhanced relative to other components and can be, in principle, discerned with improved sensitivity in the phase-resolved data obtained with n1. Experimental results in the field of heterogeneous catalysis are provided that support our findings. |
| Databáze: | OpenAIRE |
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