Room-Temperature Near-Infrared Metastable Species Measured by Phase-Sensitive Lock-in and Fourier Transform Techniques

An ultrasensitive detecting system coupled with either a lock-in or Fourier transform technique has been used to detect near-infrared (1000-2500 nm) metastable species in room temperature solutions. These species include O2(1Δg), O2(1σ+g), the solvent induced satellite peak of molecular singlet oxygen (1Δg) emission, and the triplet state of bis(triisobutylsiloxy)silicon-2,-3-naphthalocyanine (SilNC). Using the O2(1Δg) emission in benzene as a standard, the quantum yield and radiative decay rate of SiINC triplet state have been determined. Depending on types of spectral acquisition, special techniques such as phase-distinguishing and step scan capabilities were utilized. Their advantages and disadvantages are discussed.