The rotational spectrum of germyl chloride: Determination and comparison of the substitution, double substitution, and equilibrium structures

Abstract The rotational spectrum of germyl chloride has been measured up to 470 GHz. Transitions up to J = 55 and K = 24 were measured with an accuracy better than 100 kHz. The ground state rotational constants and the quartic and sextic centrifugal distortion constants have been determined accurately for 10 isotopic species in natural abundance ( 70/72/73/74/76 Ge 35 37 Cl ). Because of the presence of many isotopic species, the GeCl distance could be determined in several ways by the substitution and the double substitution methods. It is shown that the double substitution method is in general not much better than the substitution method. The high accuracy of the rotational constants allowed us to study the mass dependence of the substitution coordinate of Ge. Using the axial rotational constant and the rotation-vibration interaction constants determined by high resolution infrared spectroscopy, it was also possible to calculate a complete r e structure.