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Singlet oxygen is traditionally produced via photosensitizer molecules such as methylene blue, which function as catalysts. Here we investigate stimulated Raman generation of singlet oxygen from dissolved oxygen in both water (H2O) and heavy water (D2O) using nanosecond-pulsed visible blue laser light in the 400–440 nm spectral region without singlet oxygen photosensitizers. We report an oxygen-dependent Stokes peak in the red spectrum (600–670 nm) that is identical when produced in H2O and D2O. These red Stokes photons are not detected when an oxygen quencher is present. Temporal photodepletion of the uric acid absorbance peak at 294 nm is consistent with singlet oxygen generation. We postulate that a two-photon stimulated Raman process produces singlet oxygen from O2 dissolved within the solvents. We note that the energy difference between input and output photons of 0.97 eV is precisely the energy needed to excite O2 to its singlet state 

We propose that Raman excitation can generate singlet oxygen in water environments without intervention of photosensitizers. Preliminary Raman experiments using continuous wave laser light at 405 nm validate the hypothesis 

We measure and calibrate the photothermal spectra of Gallium Arsenide and Cadmium Telluride in the 400-800 nm spectral region using a white light source. The spectra yield the photothermal quantum yields of the materials. 

We detect the generation of enhancer-free singlet oxygen in distilled water and heavy water upon illumination with 405-nm laser radiation by measuring the quenching of the uric acid spectral peak at 294 nm. 

This contribution introduces a pump-probe photothermal mirror Z-scan method to measure the thermal quantum yield, the thermal diffusivity, and other photothermal parameters of an opaque solid. The focusing of a pump beam of light onto the sample generates thermoelastic surface distortions. The distorted surface acts as a mirror affecting the diffraction pattern of a reflected probe beam yielding the experimental signal. Scanning the focusing lens produces a single peak photothermal mirror Z-scan signature. The amplitude and time evolution of the signal determines the sample’s photothermal properties. The method is used to analyze gallium arsenide and silicon plates, obtaining good agreement with previous studies. 

We demonstrate the generation of singlet oxygen in a laser virus inactivation experiment using a low power diode light at 405 nm by detecting photobleaching of the absorption peak of uric acid at 294 nm.