Microwave Spectrum, Spectroscopic Constants, and Electric Dipole Moment of Li6F19

Transitions between the J = 1 and J = 0 rotational states of Li⁶F¹⁹ have been measured by means of the molecular‐beam electric resonance method in the four lowest vibrational states. By this means the rotational constants of Li⁶F¹⁹ were determined. These enabled one to properly assign the rotationally resolved infrared vibration—rotation spectrum of Li⁷F¹⁹ observed by Vidale and to determine the correct vibrational constants. Transitions between the M = 0 and | M | = 1 orientations of the J = 1 rotational state of Li⁶F¹⁹ in the four lowest vibrational states in a strong electric field were measured to high precision, which enabled one to determine the dipole moments accurately and to observe a nonlinear variation of dipole moment with vibrational state. The molecular constants obtained for Li⁶F¹⁹ were: $$\begin{array}{c}{B}_v\text{=45.2308111−0.7223089(v+}\frac{1}{2}\text{)+0.0058270(v+}\frac{1}{2}{)}^2\text{±0.0000050\hspace{0.17em}}\mathrm{Gc},\\ {\omega }_v\text{=964.07−8.895(v+}\frac{1}{2}){\mathrm{cm}}^{\text{−1}},\\ r_e\text{=1.563892±0.000050\hspace{0.17em}Å,}\\ {\mu }_v\text{={6.28446+0.08612(v+}\frac{1}{2}\text{)+0.00060(v+}\frac{1}{2}{)}^2\text{}±0.00100\hspace{0.17em}}\mathrm{D}.\end{array}$$