Refinements in the vibration frequencies of H3+ and D3+

Refinements in vibration intervals of the order of 1 per cent are reported for H3+ and D3+. These improved intervals result from the addition of polarization terms to the electronic wavefunction previously obtained with a complete configuration-interaction treatment of electron correlation using a 21 floating gaussian lobe basis. Twelve additional floating gaussian lobe orbitals were used to construct 78 additional configuration-interaction functions. Positions and exponents of these additional floating gaussian lobe orbitals were carefully chosen to allow for polarization of the correlated wavefunctions. Calculated vibrational state-averaged and observed geometries for H3+ agree to within 0.01 A; refined fundamental frequencies are νsub(A) = 3220.48 and νsub(E) = 2545.99 cm-1 for H3+, and νsub(A) = 2332.94 and νsub(E) = 1848.12 cm-1 for D3+. Einstein coefficients for spontaneous emission of radiation from infrared active states of H3+ and D3+ are reported, and an alternative to the Carney-Porter method of vibration analysis is used to confirm the accuracy of their method for axial molecules such as H3+. (author)