How to Isolate Potential-sensitive IR Absorption

Differential techniques The change in IR absorption associated with a change in potential can be determined through two main families of techniques. The most straightforward method consists in successively recording IR spectra for two distinct values of the potential, say Vi and V2, and taking the difference of the two spectra, or more precisely the change in absorbance where 

Modulation techniques For reversible systems, a more suitable kind of method consists in using a potential modulation coupled with a phase-sensitive detection (lock-in amplifier) the potential may be modulated, for example, as a square wave between Vj and V2 and the signal from the detector may be sent to a lock-in amplifier. The signal from the lock-in provides a function A1((t) (change in intensity reaching the detector associated with the modulation), the average intensity 1(a) being measured either simultaneously or sequentially. The 

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