THE MICROWAVE SPECTRUM AND STRUCTURE OF OZONE

Author Institution: Westinghouse Research LaboratoriesA brief review will be given of the work on $0^{16}_{3}$ reported previously by this author. Ozone is a slightly asymmetric top with the dipole moment at right angles to the top axis. Molecules of this type give complicated and unordered rotational spectra. The spectrum shows that ozone is an isosceles triangle with the apex angle between $116.5^{\circ}$ and $117^{\circ}$ and the length of the two equal sides between 1.276 and 1.279\AA. The spectrum changes very rapidly with changes in the apex angle. Centrifugal distortion effects are apparently not very large. The spectra of ozone samples containing 1.5 and 30 percent $0^{18}$ have recently been measured between 9,000 and 45,000 Mc. Three low J lines have been found for each of the following molecules: $0^{16} 0^{16} 0^{18}, 0^{16} 0^{18} 0^{16}$, and $0^{16} 0^{18} 0^{18}$. By using two of the low J lines for each molecule and a suitable range of the asymmetry parameter, constants have been determined which predict almost all lines to within 150 Mc of observed lines. This is possible because the centrifugal distortion effect is usually not greater than 150 Mc. $0^{16}_{3}$ and $0^{16} 0^{18} 0^{16}$ obey the selection rules for a triatomic molecule in the form of an isosceles triangle with identical atoms of zero nuclear spin in the base positions. The structures calculated from the spectral constants are very close to that for $0^{16}_{3}$, thus confirming the model for $0^{16}_{3}$. The dipole moment for $0^{16}_{3}$ has been determined to be $0.58 \pm .03$ Debye units