Measurement of the rotational spectrum of the water cation (H2O+) by laser magnetic resonance

Nine rotational transitions of v=0 X̃ 2B1 H2O+ have been measured by laser magnetic resonance. Optical combination differences have been combined with the LMR data in a weighted least-squares analysis using a Watson S-reduced rotational-fine structure Hamiltonian. Twenty-four molecular constants were simultaneously determined, including three hyperfine parameters and the axial components of both the anisotropic and rotational g tensors. The anisotropic g tensors are compared with their calculated values using the Curl relationship. An r0 structure was determined and is in good agreement with several ab initio results.