Localized and delocalized bound states of the main isotopologue 48O3 and of 18O-enriched 50O3 isotopomers of the ozone molecule near the dissociation threshold

Abstract

Knowledge of highly excited rovibrational states of ozone isotopologues is of key importance for modelling the dynamics of exchange reactions, for understanding longstanding problems related to isotopic anomalies of the ozone formation, and for analyses of extra-sensitive laser spectral experiments currently in progress. This work is devoted to new theoretical study of high-energy states for the main isotopologue ⁴⁸O₃ = ¹⁶O¹⁶O¹⁶O and for the family of ¹⁸O-enriched isotopomers ⁵⁰O₃ = {¹⁶O¹⁶O¹⁸O, ¹⁶O¹⁸O¹⁶O, ¹⁸O¹⁶O¹⁶O} of the ozone molecule considered using a full-symmetry approach. Energies and wave functions of bound states near the dissociation threshold are computed in hyperspherical coordinates accounting for the permutation symmetry of three identical nuclei in ⁴⁸O₃ and of two identical nuclei in ⁵⁰O₃, using the most accurate potential energy surface available now. The obtained vibrational band centers agree with observed ones with the root-mean-squares deviation of about 1 cm⁻¹, making the results appropriate for assignments and analyses of future experimental spectra. The levels delocalized between the three potential wells of ozone isomers are computed and analyzed. The states situated deep in the three (for ⁴⁸O₃) or two (for ⁵⁰O₃) equivalent potential wells have similar energies with negligible splitting. However, the states situated just below the potential barriers separating the wells, are split due to the tunneling between the wells resulting in the splitting of rovibrational sub-bands. We evaluate the amplitudes of the corresponding effects and consider possible perturbations in vibration–rotation bands due to interactions between three potential wells. Theoretical predictions for the splitting of observable band centers are provided for the first time.