1：Experimental Design and Method Selection:

The study utilized absorption spectroscopy in the deep ultraviolet range (186–196 nm) for oxygen and pressure sensing. Differential optical absorption spectroscopy (DOAS) was employed to describe oxygen concentration.

2：Sample Selection and Data Sources:

Oxygen at a concentration of 3% and high purity nitrogen were used to prepare different calibration concentrations. Air with an oxygen content of about 20.9% by volume was used for pressure measurement.

3：9% by volume was used for pressure measurement. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: A deuterium lamp (Hamamatsu 5601, Japan) as the light source, quartz lens for light collimation, a 40-cm long sample cell, USB spectrometer (Ocean Optics Maya2000), and mass flowmeters (Sevenstar, D07-19C) for gas proportion control.

4：Experimental Procedures and Operational Workflow:

Light from the deuterium lamp was collimated, passed through the sample cell, and then coupled into the spectrometer. A LabVIEW-based software was used for data collection and processing.

5：Data Analysis Methods:

The Beer-Lambert law was used for the computation of absorption cross-section. The relationship between optical parameter (OP), oxygen concentration, and pressure was analyzed.