Modulated Excitation Infrared Spectrophotometer

Abstract

The design and construction of a modulated excitation infrared spectrophotometer that allows detection of photoinduced transients in the spectral range 3000–4000 cm−1 is described. The lifetime range of photoproduced species is 10−1–10−5 sec. Information about kinetics may be obtained by amplitude and phase measurements. The sensitivity achievable by single and double modulation is discussed in detail. Performance of the instrument is illustrated by detection of four transient photoproducts of pyrocatechol, distinguishable by phase measurements. Estimated lifetimes are within 1 msec and 40 msec.