Radio-Frequency Spectrum of the a (3)Pi State of Carbon Monoxide

A preliminary investigation of the molecular-beam electric resonance spectrum of the metastable a (3)Pi state of (CO)-C-12-O-16 is reported. The electric dipole moment observed is 1.38 +/- 0.02 D. The variation of dipole moment with vibrational state appears to be less than 0.005 D per vibration. Lambda doubling values in the Omega=2 fine structure component are reported for J=2, 3, and 4. The population distribution among vibrational states resulting from excitation by 11-V electrons is in good agreement with calculated Franck-Condon factors.