BOUND-STATES AND RESONANCES OF THE HYDROPEROXYL RADICAL HO2 - AN ACCURATE QUANTUM-MECHANICAL CALCULATION USING FILTER DIAGONALIZATION

An accurate calculation of bound and resonance spectra of the non-rota ting odd O-2 exchange symmetry HO2 radical is presented. The calculati on has been carried out by a recently developed iterative technique wh ich uses filter diagonalization of a sparse matrix of the system Hamil tonian with absorbing boundary conditions, We were able to obtain 361 bound states and some 232 isolatable resonances (Gamma<0.01 eV) in a w ide energy range corresponding to the HO2-->H+O-2 unimolecular decompo sition reaction. It is shown that all resonances found have the same n ature as the bound states in that they ail are localized in the same r egion of space over the deep potential well, and moreover the extrapol ated smoothed density of the bound states merges easily with the smoot hed density of the resonance states. The level statistics for both bou nd and resonance states indicates a highly chaotic regime consistent w ith the random matrix theory. Strong mode mixing makes assignments of most bound and resonance states impossible because the corresponding w ave functions do not show any simple pattern. Interestingly, the rando mly fluctuating high resolution density of states after smoothing show s a structure resembling two basic frequencies corresponding to the O- 2 stretch and HOO bend motion of the HO2 molecule. (C) 1995 American I nstitute of Physics.