MICROWAVE SPECTRUM OF DIMETHYLGERMANE

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 A (assumed), ∠HCH=108.5° (assumed), rCGe=1.950±0.003 Å, ∠CGeC=110.0±0.5°. No tilt of the methyl groups was detected.