Observation of the Zeeman Effect of Ozone by Doppler Free Laser Spectroscopy

During the past decade laser magnetic resonance has become a powerful tool in molecular spectroscopy of free radicals and molecular ions. Because of its high sensitivity it is an excellent method to investigate free radicals in very low concentrations and to measure their molecular constants with high precision. So far most of the radicals observed by radioastronomy have been investigated by LMR methods. We have begun the construction of a LMR spectrometer in order to analyze the spectra of radicals and ions of astrophysical interest by means of C 0 2 , N 2 0 and CO lasers. For a variety of reasons, ozone was chosen as first target for investigation with the newly built LMR spectrometer. (i) There exist several coincidences between strong 0 3 absorption lines and several C 0 2 laser lines [1,2, 3]. (ii) The small (rotational) magnetic moment of 0 3 allows a scrutinizing test of the spectrometer's resolution. It also demonstrates the feasibility of LMR techniques even on closed shell molecules, which are mostly not taken into consideration for LMR experiments, and (iii) In comparison with ions and radicals the handling of 0 3 is easy. Since the molecular constants [4] and the magnetic moments along the principal axes [5] are known to high accuracy, the molecular Zeeman effect of the observed transitions can be calculated using the expressions given by Huttner and Flygare [6] for asymmetric top molecules.