Der Zeemann-Effekt im Rotationsspektrum von 2-Fluoropyridin

Abstract

Abstract The molecular Zeeman effect has been observed in the rotational spectrum of 2-fluoropyridine at magnetic fields close to 25000 G. The measured molecular g-values are g aa = -0.0880 ± 0.0007, g bb = - 0.0405 ±0.0006, g cc = + 0.0233 ±0.0006, and the two linearily independant components of the magnetic susceptibility anisotropy are 2 · χ aa - χ bb - χ cc = 50.5 ± 1.6 and 2 · χ bb - χ cc - χ aa - 53.8 ± 1.1 in units of 10 -6 erg/G 2 mol). The a-axis is close to the C-F-bond and the c-axis is perpendicular to the plane of the ring. A comparison of the gas-phase out-of-plane minus the average in-plane values for the susceptibilities of 2-fluoropyridine, pyridine, and fluorobenzene with the corresponding value for benzene in crystalline phase leads to the conclusion that the susceptibilities may change in the order of 10% when going from solid or liquid phase to the gasphase. A short description of the microwave-Zeeman spectrograph built at Kiel University is given. In the theoretical section expressions for the g-values and susceptibilities are derived which are more complete then those used up to now.