Abstract
We discuss experimental and theoretical results of absorption features of the oxygen A-band transitions in the optically thick regime when synchronous detection at higher harmonics (N≥2), using wavelength modulation spectroscopy (WMS), is performed. We show that the absorption saturation effects demonstrate a distinctive feature which results in suppression of the line-center lobes of the harmonic signals. These effects depend on the optical pathlength as well as on the modulation index. The rich structure of WMS signals, especially at higher detection orders, is central to the technique’s advantages in resolving spectra congested with highly disparate oscillator-strength lines. The effect of pathlength saturation on this structure is investigated.
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Amir Khan, M., Mohan, K. & Dharamsi, A.N. Optical pathlength saturation signatures in wavelength modulation spectroscopy signals of atmospheric molecular oxygen. Appl. Phys. B 99, 363–369 (2010). https://doi.org/10.1007/s00340-009-3814-3
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DOI: https://doi.org/10.1007/s00340-009-3814-3