High precision measurement of ultraweak transitions of the a${^1}{\triangle}_g{\leftarrow}$X $^3{\Sigma}^{-}_g$ $(0,0)$ band of molecular oxygen

TL;DR

This study employs cavity-enhanced frequency modulation spectroscopy to precisely measure ultraweak quadrupole transitions of molecular oxygen's (0,0) band, providing detailed parameters like line widths and intensities for different isotopes and pressures.

Contribution

It introduces a highly sensitive measurement technique for ultraweak oxygen transitions, yielding new data on line widths and intensities that align with recent theoretical predictions.

Findings

Measured self- and air-broadened half-widths at multiple pressures

Determined line intensities for $^{16}$O$_2$ and $^{18}$O$_2$

Results agree with recent theoretical calculations

Abstract

We have used a highly sensitive cavity-enhanced frequency modulation spectroscopy technique to measure different parameters of the ultraweak transitions of a${^1}{\triangle}_g{\leftarrow}$X $^3{\Sigma}^{-}_g$ $(0,0)$ band of molecular oxygen in the range 7640 cm$^{-1}$ to 7917 cm$^{-1}$. The self-broadened half-width and air-broadened half-width of the transitions have been measured for three different pressures for both $^{16}$O$_2$ and $^{18}$O$_2$. To measure the line intensity and self-broadened half-width we have used ultra pure oxygen sample and air-broadened half-width was measured with dry air sample. The $(0,0)$ band of $^{16}$O$_2$ and $^{18}$O$_2$ show weak quadrupole transitions with line intensities ranging from $1\times10^{-30}$ to $1.9\times10^{-28}$ cm/molecule. The measurements are in excellent agreement with the recent measurement of Rothman et. al