Revisiting spontaneous Raman scattering for direct oxygen atom quantification.

Area of Science:

• Atomic Physics
• Plasma Science
• Spectroscopy

Background:

• The Raman activity of oxygen atoms is largely unexplored for quantitative measurements.
• Accurate methods are needed to determine absolute densities in gases with oxygen atoms.

Purpose of the Study:

• To evaluate the potential of oxygen atom Raman activity for determining absolute gas densities.
• To establish accurate cross sections for specific oxygen atom transitions ($^3P_2 o ^3P_1$ and $^3P_2 o ^3P_0$).

Main Methods:

• Utilized carbon dioxide microwave plasma to create a self-calibrating gas mixture.
• Employed Raman spectroscopy to measure cross sections for oxygen atom transitions.
• Validated stoichiometric conservation using a 1D fluid model.

Main Results:

• Measured cross sections: $\sigma_{J=2\to1} = 5.27 \pm _{sys:0.53}^{rand:0.17} \times 10^{-31}\;cm^2/sr$ and $\sigma_{J=2\to0} = 2.11 \pm _{sys:0.21}^{rand:0.06} \times 10^{-31}\;cm^2/sr$.
• Achieved a detection limit of $1 \times 10^{15}\;cm^{-3}$ in systems without other scattering species.

Conclusions:

• Oxygen atom Raman activity is a viable method for determining absolute densities in oxygen-containing gases.
• The established cross sections provide a foundation for future quantitative Raman spectroscopy of oxygen atoms.