Fourier transform spectrometer remote sensing of O2 A-band electric quadrupole transitions

We observed electric quadrupole transitions in the O2 A-band, b1Σg+←X3Σg−(0,0), in high solar zenith angle atmospheric spectra recorded with the high-resolution solar-viewing Fourier transform spectrometer at Park Falls, WI. We identified 12 ΔN=±3 transitions for the first time, including the first detection of NO-branch transitions and extended the TS-branch observations of Brault [J Mol Spectrosc 1980;80:384-8] up to N″=23. Additionally, we observed six electric quadrupole transitions of the ΔN=−1 PO-branch. These observations demonstrate the excellent sensitivity and long-term stability of the new generation of solar-viewing Fourier transform spectrometers.

► Observed O2b1Σg+←X3Σg−(0,0) electric quadrupole (EQ) transitions. ► Found 19 previously unobserved ΔN=±3, ±1 EQ transitions. ► These transitions are among the weakest yet studied by remote sensing. ► Emphasizes the value of high-resolution, solar-viewing Fourier transform spectroscopy.