Application of Laser Magnetic Resonance Spectroscopy to the Measurement of Electric Dipole Moment of Free Radicals

An intracavity CO laser magnetic resonance spectrometer with homogeneous dc electric field applied via a pair of parallel Stark plates in the absorption cell is used to measure the electric dipole moments of free radicals. Taking advantage of the high sensitivity and high resolution of this technique and the Stark effect, highly-resolved saturated absorption spectra of the ν = 1-0 transition of 15N16O in the ground state X2Π3/2 have been successfully observed in the presence of a low electric field. The electric dipole moment of NO in the electronic ground state is determined as µ = 0.1566±14 D (Debye) from the analysis of the observed spectra, confirming that, combined with the Stark field, the laser magnetic resonance technique can be an effective and reliable approach for the precise measurement of electric dipole moments of free radicals, especially unstable ones.