Observation ofπStark Components in Microwave Spectroscopy: Precision Measurements on HCN

A parallel plate Stark cell has been designed and constructed for the millimeter wave region of the spectrum. With the cell both $\pi$ and $\sigma$ Stark components can be observed. High precision Stark effect measurements have been made on the $\pi$ and $\sigma$ components of the $J=0\mathrm{}\to 1$ transition of HC${\mathrm{N}}^{14}$. From these the electric dipole moment of HCN in the ground vibrational state has been calculated to be 2.985±0.005 Debye units.