A comparative rotational analysis of the 0 00 bands of the 3A 2← [formula omitted]1A 1 Wulf transition for the isotopomers 16O 3 and 18O 3 of ozone by high resolution Fourier transform spectrometry

Abstract

A high resolution Fourier transform spectrometry comparative analysis of the rotational structure of the 0 0 0 absorption band of the 3A 2← X ̃ 1A 1 Wulf transition for the isotopomers 16O 3 and 18O 3 of the ozone molecule is presented. With a near pure case (b) coupling model for the upper triplet state, we identified, in these two rovibrational bands, numerous lines of sub-bands associated with the three F 1( N= J−1), F 2( N= J), F 3( N= J+1) spin components. Many superpositions around the origin, plus perturbations and predissociation phenomena limit our unperturbed data set for the 3A 2 state to less than 100 unperturbed rotational lines in the range 9100–9550 cm −1 for each band. Using for each of them the well defined ground state parameters, we obtained a standard deviation of about 0.050 cm −1 in the fits to the lines. The rotational constants A, B, C, the three rotational distortion terms Δ K, Δ K, Δ J, the spin-rotation constants a 0, a, and b and the spin-spin constant α are determined for the (0 0 0) vibrational level of the 3A 2 state and of the two isotopomers. The parameter β arbitrarily fixed for 16O 3 was successfully calculated for 18O 3 and this last result justifies the β value adopted for 16O 3. The geometrical parameters of the 3A 2 state for the two isotopomers are close, r=1.343 Å, θ=98.8° for 18O 3 and r=1.345 Å, and θ=98.9° for 16O 3. So are the Δ and κ values. The origin of the 18O 3 0 0 0 band is blue shifted by 20.6(4) cm −1 with respect to the 16O 3 0 0 0 band. For the congested parts of the spectra comparisons of both isotopic species has to be done in a special way through sub-band contours. We justify the existence of perturbations in the first vibrational levels of the 3A 2 state by several crossings with high vibrational levels of the ground state.