Molecular Dipole Moments and Stark Effects I. Stark Effects on Symmetric Top Molecules with Nuclear Quadrupole Coupling

The hyperfine structure of rotational levels of a symmetric top molecule in which one nucleus has an electric quadrupole moment is derived for weak, strong, and intermediate fields. Intensities of the hyperfine components are discussed. Solution of a second-order secular equation is shown to suffice for the evaluation of dipole moments from microwave spectra. A sample calculation is given for nuclear spin of $\frac{3}{2}$ and $J=1\mathrm{}\to 2$ transition.