Knowledge Bank

High-resolution microwave spectroscopy is combined with high magnetic fields (up to 30,000 gauss over a 6 foot length) to yield resolvable first-order (H) and second order $(H2)$ Zeeman spectra in a large number of molecules. The magnet and phase locked microwave spectrograph ($2.0-40.0$ gHz) will be described briefly. The molecular Zeeman effect has been observed in fluoroacetylene, methylacetylene, and methyldiacetylene. The molecular g-values and magnetic susceptibility anisotropies are given which lead to the second moment of the electronic charge distribution and molecular quadrupole moments. The magnetic properties of these molecules will be discussed in light of recent work on $CH3CN$ and $CH3NC$. The possible additivity of group magnetic susceptibilities will also be discussed.