Juan R. Pardo-Carrion
Abstract N. 2

J.R. Pardo, L. Pagani, M. Gerin and C. Prigent; 1995.

"Evidence of the Zeeman Splitting in the 2(1)->0(1) Rotational Transition of the atmospheric 16O18O Molecule from Ground-Based Measurements"

J. Quant. Spectr. and Radiat. Transfer, 54, N6, 931-943.


We present in this paper a set of spectra of the atmospheric 16O18O molecule taken at 233.94611 GHz with the 2.5-m radiotelescope POM-2 located at Plateau de Bure (Lat. 44:38:02.00 N, Long. 5:54:28.50 E, Alt. 2550 m) in the French Alps. These spectra clearly show a Zeeman substructure over a +/- 2.5 MHz range from the line centre. The central frequencies for each peak would indicate local mean values of the geomagnetic field over Plateau de Bure for the altitude range 2.5-130 km of around 40 micro-Tesla that a slight, but measurable, difference with respect to a standard geomagnetic field based on measurements carried out in 1980, that gives values around 44 micro-Tesla. Depending on the direction and polarization we see 2, 4, or 6 peaks that are identified as Pi (Delta_M=0) or sigma+/- (Delta_M=+/-1) components. This effect cannot be seen from ground-based measurements in the millimetric lines of the main isotope 16O2 for which very broad emission and high opacity of low layers eliminates any structure, but it must be taken into account for atmospheric temperature soundings from satellite at frequencies close to these 16O2 resonances.