A spectroscopic study of CaOCH₃ using the pump/probe microwave and the molecular beam/optical Stark techniques

The Stark effect on the ^qR₂₂(0,0.5) (ν=17682.9251cm^-1) and ^qP₁₁(0,1.5) (ν=17682.1966cm^-1) branch features of the (0,0) B²A₁-X²A₁ band system of calcium methoxide, CaOCH₃, was measured and analyzed to give the magnitude of the permanent electronic dipole moments, μ, of 1.58(8) D and 1.21(5) D for the X²A₁ and B²A₁ states, respectively. The dipole moments are compared with other monovalent calcium compounds and those predicted from a simple electrostatic model. Pure rotational transitions in the X²A₁ state were recorded using the pump/probe microwave-optical double resonance technique. The proton magnetic hyperfine splitting pattern confirms a C_3v symmetry of the ground electronic state. The determined Fermi contact and dipolar parameters are: a_F=-0.421(27)MHz; T_aa=1.070(45)MHz, and T_bb-T_cc=0.292(47)MHz. The latter parameter is associated with the lifting of the K-degeneracy of this symmetric top molecule and mixing the I₀=1/2 and I₀=3/2 levels.