Radio Frequency Spectrum of the X 2π State of 7Li16O

The molecular beam electric resonance spectrum of the high temperature free radical ⁷Li¹⁶O is measured in areas of the region 5–12 350 MHz. ΔJ=0, ΔF=0, ±1 electric dipole transitions are observed in the ${}^2{\Pi }_{\text{3/2}}$ and ${}^2{\Pi }_{\text{1/2}}$ spin—orbit components of the ground electronic state. Transitions of the two lowest vibrational states are analyzed. The fine structure parameters are: $$\begin{array}{cccc}& \text{v=0}& & \text{v=1}\\ A_{\Pi }& \text{−112.0(1)\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}& & \text{−108(1)\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}\\ {\text{〈 Π | (A/2+B)L}}^{+}{\mathrm{|\; \Sigma \; 〉\; 〈\; \Pi \; |\; BL}}^{+}\mathrm{|\; \Sigma \; 〉}& \text{−139.3(2)}\mathrm{c}{\mathrm{m}}^{\text{−1}}& & \text{−139.5(2.0)\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}\\ {\omega }_e& & \text{800(100)\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}& \\ \mu & \text{6.84(3)\hspace{0.17em}}\mathrm{D}.& & \end{array}$$ The Frosch and Foley hyperfine parameters are: $$\begin{array}{ccc}{a}_{\Pi }{\text{+ 1/2\hspace{0.17em}(b}}_{\Pi }{\mathrm{+\; c}}_{\Pi })& \text{3.98(1)\hspace{0.17em}}\mathrm{MHz}& \text{3.83(3)\hspace{0.17em}}\mathrm{MHz}\\ a_{\Pi }{\text{− 1/2\hspace{0.17em}(b}}_{\Pi }{\mathrm{+\; c}}_{\Pi })& \text{8.25(4)\hspace{0.17em}}\mathrm{MHz}& \text{6.76(8)\hspace{0.17em}}\mathrm{MHz}\\ b_{\Pi }& \text{−19.67(14)\hspace{0.17em}}\mathrm{MHz}& \text{−20.2(5)\hspace{0.17em}}\mathrm{MHz}\\ d_{\Pi }& \text{1.94(10)\hspace{0.17em}}\mathrm{MHz}& \text{1.65(3)\hspace{0.17em}}\mathrm{MHz}\\ {\mathrm{〈\; \Pi \; |\; aL}}^{+}\mathrm{|\; \Sigma \; 〉}& \text{−11.0(1.4)\hspace{0.17em}}\mathrm{MHz}& \\ {\mathrm{eQq}}_0& \text{0.444(8)\hspace{0.17em}}\mathrm{MHz}& \\ {\mathrm{eQq}}_2& \text{0.109(18)\hspace{0.17em}}\mathrm{MHz}.& \end{array}$$ The observed fine structure constants are in excellent agreement with Van Vleck's model of pure precession and with detailed calculations of Wahl.