Confirming the stimulated Raman origin of singlet‐oxygen photogeneration

Abstract

AbstractWe confirm the Raman origin of the singlet oxygen photogenerated in water environments without using photosensitizers. Nanosecond light pulses in the blue region of the spectra (405–480 nm) generate Raman Stokes excitation of singlet oxygen in the red region (600–670 nm) when focusing on pure distilled water. The excitation also produces Stokes components corresponding to the stretching modes of water molecules. The time evolution of both types of Stokes components, singlet oxygen, and stretching modes correspond to the time duration of the excitation pulse as expected for a Raman process. Their power dependences are also similar. Finally, both signals exhibit high refractive ring structures due to the nonlinear optical interaction generated by the stimulated Raman process.