Accurate absolute absorption cross-sections of the ozone Wulf bands at 1 µm range: measurements with high-resolution cw-CRDS laser techniques

Abstract

Ozone plays a major role in atmospheric chemistry and radiative processes with an impact on climate and ecosystems being also considered as a possible biosignature species in exoplanetary observations. This makes important an extension of accurate laboratory data to various spectral ranges. The present work provides absolute absorption cross-sections of ozone accurate to about 3% in the near-IR range around 1 µm using for the first time a continuous-wave cavity-ring-down spectrometer (cw-CRDS) for recording the transitions above the first dissociation threshold of O3. This has permitted high-sensitivity and high-resolution measurements covering the region from 9745 to 10850 cm−1 corresponding to the transitions from the electronic ground state to spin-rovibronic levels of excited triplet electronic states 3A2 and 3B2 that form the Wulf band system. Two complementary methods based on the stationary recording with the quasi-continuous laser tuning and on the pressure ramp measurements at carefully chosen grids of wavenumbers were implemented and provided very well consistent results within 2% on average. The experimental integrated absorption intensity in the range under the study is evaluated as 1.393×10−20 (± 2%) cm/molecule. The comparison with the available published data of continuous recordings shows that our absorption cross-sections are much more accurate, particularly in the region with complex partly resolved spin-rovibronic spectral patterns. This region corresponds to a transparency near-IR window of the water vapor and is thus well suited for atmospheric applications. The theoretical modeling of the measured spectra using eight rovibronic bands is discussed. The experimental absorption cross-sections at the dense grid of wavenumbers are provided in the electronic supplementary files, which could be used as new reference data in the 9745 to 10850 cm−1 range.