Vibrational spectrum of Li3 first‐excited electronic doublet state: Geometric‐phase effects and statistical analysis

We present J=0 calculations of all bound and pseudobound vibrational states of Li₃ in its first‐excited electronic doublet state by using a realistic double many‐body expansion potential‐energy surface and a minimum‐residual filter diagonalization technique. The action of the system Hamiltonian on the wave function was evaluated by the spectral transform method in hyperspherical coordinates. Calculations of the vibrational spectra were carried out both without consideration and with consideration of geometric‐phase effects. Dynamic Jahn–Teller and geometric‐phase effects are found to play a significant role, while the calculated fundamental symmetric stretching frequency is larger by 8.3% than its reported experimental value of 326 cm^?1. From the neighbor‐spacing distributions of the levels, it is observed that the title vibrational spectrum is quasiregular in the short range and quasi‐irregular in the long range. By the Δ₂ standard defined in this article, it is found that the spectra are more nonuniform than those of the “trough” states for the ground electronic state. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 75: 89–109, 1999