Spatiotemporal distribution measurements of ozone in the gas and liquid phases generated by non-equilibrium atmospheric pressure radical source

The beneficial effects of plasma treatment are induced by active species of various lifetime. Especially, it is difficult to measure the temporal and special distributions of short-lived species including liquid phase as well as gas phase. To overcome the issue, we have constructed a novel measurement system that enables spatiotemporal absorption spectroscopy with high speed and spatial resolution.

In this study, we first measured spatiotemporal distribution of ozone in gas and liquid phases simultaneously by this system. The light from a light source is incident to the gas and liquid phases, where ozone is generated by radical source, and transmitted to a spectrometer and detected by ICCD camera.

The spatiotemporal distribution of absorbance calculated using every 5 sec-signal from ICCD was obtained. The absorbance in gas phase increased with increasing the distance from the exit of radical source whereas that in liquid phase had peaks around 4 and 8 mm from the liquid interface. Moreover, the absorbance disappeared 90 s in the gas phase and 20 s in the liquid phase after the end of irradiation.

The measurement system has successfully measured the dynamic distribution of absorbance in gas and liquid phases simultaneously with high spatial and speed resolutions of 13 µm and 440 µs.