Microwave Spectrum of Lithium Chloride

The rotational transitions J=0→1 in the three lowest vibrational states of Li7Cl35 and the two lowest vibrational states of Li7Cl37 have been measured at a temperature of 600°—800°C. The molecular constants (in Mc/sec) for Li7Cl35 are: Be=21181.1±0.1, αe=240.2±0.2, γe=1.2±0.2; those for Li7Cl37 are: Be=20989.9±0.1, αe=236.9±0.2. The internuclear distance is re=2.02067±0.00006 A. (The uncertainties represent maximum limits of error.) A combination of the present results with molecular beam electric resonance data yields a dipole moment μv=7.075+0.0885 (v+½) D for Li6Cl35. Two high‐temperature microwave spectrometers of new design are described briefly. A tabulation of molecular constants for the complete series of alkali halide molecules is included.