SPECTRA AND TIME-DEPENDENT DYNAMICS OF H-3 NEAR THE CONICAL INTERSECTION IN THE (2P)1 E' GROUND ELECTRONIC MANIFOLD

We report on the spectra and dynamics of H-3 near the conical intersec tion in its (2p)1E' ground electronic manifold. The time-dependent wav e packet approach and the double many-body expansion (DMBE) potential energy surface (PES) are employed for this purpose. We use Jacobi coor dinates (R,r,gamma) and employ the fast Fourier transform method for R and r, and the discrete variable representation method for gamma, in conjunction with the split-operator formalism to,describe the evolutio n of the wave packet (WP) in space and time, respectively. While the m ain focus of the present work is to explicitly reveal the effects of n onadiabatic coupling between the two sheets of the DMBE PES, companion calculations are also carried out to investigate the dynamics on the uncoupled upper and lower adiabatic sheets, both in two and three dime nsions (for total angular momentum J = 0). A set of pseudospectra is c alculated by Fourier transforming the time autocorrelation function of suitably chosen Gaussian wave packets located initially at the minimu m energy point of the seam of conical intersections. The eigenstates t hus obtained are assigned by computing their eigenfunctions by spectra l quantization. In the coupled states treatment the WP is propagated i n the diabatic representation. The time dependence of the adiabatic po pulations is calculated by using suitable adiabatic projection operato rs. We find strong effects of nonadiabatic coupling on the discrete vi brational energy levels of the upper adiabatic sheet, which all change to quasibound states in the coupled manifold. The comparison of the d ecay dynamics of various levels of the upper adiabatic sheet indicates considerable mode specificity (their lifetimes typically vary between 3 and 6 fs). On the other hand, resonances are seen to be less pronou nced near the conical intersection on the lower adiabatic sheet(when c ompared to those in the literature, obtained near the collinear saddle point region). The effect of nonadiabatic coupling on them is only mi nor. We also report preliminary results on the optical emission spectr um of H-3 and compare them with the experimental findings. (C) 1998 Am erican Institute of Physics.