Microwave Spectrum of Dimethylgermane

Abstract

The rotational spectrum of the five Ge isotopic species of dimethylgermane has been investigated in the region 8–35 GHz. All identified transitions were split into quartets by the internal rotation of the methyl groups. From the splittings a barrier $V_3\text{\hspace{0.17em}=\hspace{0.17em}1182}\mathrm{cal}/\mathrm{mole}$ has been determined. Rotational constants for the $A_1{A}_1$ ground torsional state of the ⁷⁴Ge species are $\text{A\hspace{0.17em}=\hspace{0.17em}12 522.67}\mathrm{MHz}\text{, B\hspace{0.17em}=\hspace{0.17em}5587.68}\mathrm{MHz}$ , and $\text{C\hspace{0.17em}=\hspace{0.17em}4264.57}\mathrm{MHz}$ . No hyperfine structure due to the quadrupole moment of ⁷³Ge was resolved giving upper limits ${\mathrm{|\hspace{0.17em}\chi }}_{\mathrm{aa}}\text{\hspace{0.17em}|\hspace{0.17em}<\hspace{0.17em}3.0}\mathrm{MHz}{\mathrm{,\; |\hspace{0.17em}\chi }}_{\mathrm{bb}}\text{\hspace{0.17em}|\hspace{0.17em}<\hspace{0.17em}3.6}\mathrm{MHz}$ . Stark‐effect measurements gave a dipole moment of 0.616 D. With assumption of the methyl‐group dimensions, structural parameters for the heavy atoms were calculated to be: $r_{\mathrm{CH}}\text{\hspace{0.17em}=\hspace{0.17em}1.083 Å}$ (assumed), $\angle \mathrm{HCH}\text{\hspace{0.17em}=\hspace{0.17em}108.5°}$ (assumed), $r_{\mathrm{CGe}}\text{\hspace{0.17em}=\hspace{0.17em}1.950\hspace{0.17em}±\hspace{0.17em}0.003 Å, ∠}\mathrm{CGeC}\text{\hspace{0.17em}=\hspace{0.17em}110.0\hspace{0.17em}±\hspace{0.17em}0.5°}$ . No tilt of the methyl groups was detected.