Microwave Spectrum of BaO

Transitions between the J=1 and J=0 rotational states of Ba138O16 have been measured by means of the molecular beam electric resonance technique in the four lowest vibrational states. By this means the rotational constants of BaO were determined to a high degree of accuracy. The previous excellent determination of the rotational constants of BaO by the analysis of optical spectra by Lagerqvist, Lind, and Barrow was confirmed. Additional evidence is found to support the claim that the lower state observed in the optical spectra—the state observed in this investigation—is the ground state, and this state has no net electronic angular momentum. Some of the molecular constants determined were as follows: Bv={9.371952−0.041776(v+12)−0.000120(v+12)2Gc/sec}±14 kc/sec, re=1.93966±0.00005 Å.