Microwave spectrum of the GeCl radical

Microwave spectrum of the GeCl radical in the ground vibronic state was observed for the 2Π1/2 as well as 2Π3/2 spin substate. The GeCl radical was generated in a free-space absorption cell by a dc discharge in GeCl4 diluted with Ar. The observed spectra were subjected to a least-squares analysis to yield accurate molecular constants; those of the most abundant isotopomer 74Ge35Cl are as follows; B0 = 4535.91396(70) MHz, D0 = 2.5413(13) kHz, AD0 = 4.87595(37) MHz, ∣p0∣ = 17.87(31) MHz, ∣q0∣ = 4.06(18) MHz, and ∣p0 + 2q0∣ = 25.984(39) MHz, where uncertainties given in parentheses correspond to one standard deviation. The absolute signs of p0 and q0 are indeterminable, although they have the same sign. The equilibrium rotational constant Be and the vibration-rotation interaction constant αe were derived by analyzing the mass dependence of the B0 constants for seven isotopomers. The equilibrium bond length was determined to be re = 2.163739(23) Å.