Der Zeeman-Effekt im Rotationsspektrum von Orthodifluorbenzol

The linear and quadratic rotational Zeeman effect in orthodifluorobenzene has been observed in magnetic fields up to 25 kG. The magnetic susceptibility anisotropies are χaa- (χbb -χcc)/2 = (25.4 ± 0.8)* 10 erg/(G * mole) and χbb - (χcc - χaa)/2 = (29.0±0.5)* 10 erg/ (G * mole) ; (the c-axis is perpendicular to the molecular plane and the a-axis coincides with the twofold symmetry axis of the molecule); the molecular ^-values are gaa= -0.0412 ± 0.00'I2, gbb=0.0371± 0.0008 and gcc= +0.0163 ±0.0007. A comparison of ⊿χ = χcc- (χaa + χbb)/2 with the corresponding values of related compounds, part of which were determined by the Cotton-Mouton technique, indicates that the effect of the magnetic field on the electric polarizability of benzene - like molecules is in the order of - 1 * 10 cm /G and should be accounted for in the evaluation of Cotton- Mouton data.