H 3 + : Geometry dependence of electronic properties

As the first step to the ab initio calculation of the vibration-rotation spectrum of the H3+ ion, we present results of configuration-interaction calculations of the potential-energy surface and the geometry-dependent electric dipole and quadrupole moments for the ground electronic state. Interpolation on the potential-energy surface, required for setting up the Hamiltonian matrix for nuclear motion, is facilitated by use of generalized Morse functions and Fourier analysis. An analysis of the equilibrium geometry and harmonic force constants is based upon the present and previous calculations. We conclude that H3+ has its potential minimum in an equilateral geometry with bond distances of 1.65 a.u. and harmonic frequencies ωA=3471 cm−1 and ωE=2814 cm−1.