Vibrationally and rotationally nonadiabatic calculations on H ₃⁺ using coordinate-dependent vibrational and rotational masses

Using the core-mass approach, we have generated a vibrational-mass surface for the triatomic H₃⁺. The coordinate-dependent masses account for the off-resonance nonadiabatic coupling and permit a very accurate determination of the rovibrational states using a single potential energy surface. The new, high-precision measurements of 12 rovibrational transitions in the ν₂ bending fundamental of H₃⁺ by Wu are used to scale this surface empirically and to derive state-dependent vibrational and rotational masses that reproduce the experimental transition energies to 10^-3cm^-1. Rotational term values for J≤10 are presented for the two lowest vibrational states and equivalent transitions in D₃⁺ considered.