Radio-Frequency and Microwave Spectra of LiBr by the Molecular-Beam Electric-Resonance Method

The molecular‐beam electric‐resonance technique has been used to obtain dipole moments μ_v, quadrupole interaction constants of bromine (eqQ)_v, spin—rotation interaction constants c_Br, and rotational constants for ⁶Li⁷⁹Br and ⁶Li⁸¹Br in several of the lower vibrational levels. The observation of J=1 radio‐frequency spectra for three or more vibrational states led to the following values: $$\begin{array}{c}{\mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}}^6{\mathrm{Li}}^{79}\mathrm{Br}\\ {\mu }_v\text{=7.22624+0.08318(v+}\frac{1}{2}\text{)+0.00057(v+}\frac{1}{2}{)}^2\text{±0.001\hspace{0.17em}\hspace{0.17em}}\mathrm{D},\\ {\mathrm{(eqQ)}}_v\text{=37.015+2.918(v+}\frac{1}{2}\text{)−0.039(v+}\frac{1}{2}{)}^2\text{±0.005\hspace{0.17em}}\mathrm{Mc}/\sec ,\\ c_{\mathrm{Br}}\text{=9.2±0.2\hspace{0.17em}}\mathrm{kc}/\sec .\\ {\mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}}^6{\mathrm{Li}}^{81}\mathrm{Br}\\ {\mu }_v\text{=7.22611+0.08312(v+}\frac{1}{2}\text{)+0.00060(v+}\frac{1}{2}{)}^2\text{±0.001\hspace{0.17em}\hspace{0.17em}}\mathrm{D},\\ {\mathrm{(eqQ)}}_v\text{=30.912+2.442(v+}\frac{1}{2}\text{)−0.034(v+}\frac{1}{2}{)}^2\text{±0.005\hspace{0.17em}}\mathrm{Mc}/\sec ,\\ c_{\mathrm{Br}}\text{=9.9±0.2\hspace{0.17em}}\mathrm{kc}/\sec .\end{array}$$ The observation of J=1→J=0 microwave transitions yielded the following rotational constants: $$\begin{array}{cc}{}^6{\mathrm{Li}}^{79}\mathrm{Br}\mathrm{\hspace{0.17em}(}\mathrm{Mc}/\sec )& {}^6{\mathrm{Li}}^{81}\mathrm{Br}\mathrm{\hspace{0.17em}(}\mathrm{Mc}/\sec )\\ B_0\text{=19 090.296±0.006,}& B_0\text{=19 057.005±0.006,}\\ B_1\text{=18 882.800±0.009,}& B_1\text{=18 850.050±0.020,}\\ B_2\text{=18 677.242±0.055.}& B_2\text{=18 645.035±0.217.}\end{array}$$