Refinements in the vibration frequencies of H3+and D3+

Abstract

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 Å; refined fundamental frequencies are v_A = 3220·48 and v_E = 2545·99 cm^-1 for H₃ ⁺, and v_A = 2332·94 and v_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 ⁺.