Microwave Spectrum of Dimethylgermane

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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 V3 = 1182 cal/mole has been determined. Rotational constants for the A1A1 ground torsional state of the 74Ge species are A = 12 522.67 MHz, B = 5587.68 MHz, and C = 4264.57 MHz. No hyperfine structure due to the quadrupole moment of 73Ge was resolved giving upper limits | χaa | < 3.0 MHz, | χbb | < 3.6 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: rCH = 1.083 Å (assumed), ∠HCH = 108.5° (assumed), rCGe = 1.950 ± 0.003 Å, ∠CGeC = 110.0 ± 0.5°. No tilt of the methyl groups was detected.