Analysis of the CRDS spectrum of 18O3 between 6950 and 7125 cm−1

The absorption spectrum of the 18O3 isotopologue of ozone was recorded by CW-Cavity Ring Down Spectroscopy in the 6950-7125 cm−1 region. The typical noise equivalent absorption of the recordings is αmin ≈1×10−10 cm−1. The spectrum is dominated by three very weak bands: 3ν1+5ν3 near 7009 cm−1 and the ν2+7ν3 and 4ν2+5ν3 interacting bands near 7100 cm−1. In total 260, 206 and 133 transitions were assigned for the 3ν1+5ν3, ν2+7ν3 and 4ν2+5ν3 bands, respectively. The line positions of the 3ν1+5ν3 band were modelled using an effective Hamiltonian (EH) model involving two dark states - (6 0 1) and (2 5 2) - in interaction with the (3 0 5) bright state. The EH model developed for the ν2+7ν3 and 4ν2+5ν3 bands involves only the (0 1 7) and (0 4 5) interacting bright states. Line positions could be reproduced with rms deviations on the order of 0.01 cm−1 and the dipole transition moment parameters were determined for the three observed bands. The obtained set of parameters and the experimentally determined energy levels were used to generate a list of 984 transitions of the three bands which is provided as Supplementary Material.

► High sensitivity Cavity Ring Down Spectroscopy of 18O3 between 6950 and 7125 cm−1.► 599 transitions were assigned to the 3ν1+5ν3, ν2+7ν3 and 4ν2+5ν3 bands. ► Highest vibrational bands of 18O3 in the electronic ground state analysed so far.